ENGINEERING  LIBRARY 


MODERN   METHODS   OF  WELDING 


METHODS  OF  WELDING 

AS   APPLIED    TO 

WORKSHOP    PRACTICE 

DESCRIBING   VARIOUS    METHODS 


OXY-ACETYLENE  WELDING  ELECTRIC  SEAM  WELDING 

OXY-HYDROGEN  WELDING  ELECTRIC  SPOT  WELDING 

LEAD  BURNING  MIRROR  WELDING 

THERMIT  WELDING  CUTTING  IRON  AND  STEEL 

ELECTRIC  ARC  WELDING  EYE-PROTECTION    IN    WELD- 
ELECTRIC  BUTT  WELDING  ING  OPERATIONS 
AMERICAN  METHODS 


BY 


J.    H.    DA  VIES 

J  n 

LEEDS    TECHNICAL    SCHOOL    AND    CONSULTING   ENGINEER 


NEW  YORK 

D.  VAN  NOSTRAND  COMPANY 

EIGHT  WARREN  STREET 

1922 


Engineering 
Library 


PRINTED    IN    GREAT    BRITAIN    BY    BILLING   AND    SONS,    LTD. 
GUILDFORD    AND    ESHER 


PREFACE 

WE  live  in  a  world  of  wonders.  The  life  of  each  one  of  us  is,  of 
necessity,  so  hemmed  in  by  circumstances  that  none  can  see  much 
beyond  the  bounds  of  his  own  habitat.  We  recognise  the  progress 
of  an  industry  which  comes  within  our  own  experience,  but  we  know 
little  of  those  with  which  we  are  not  in  personal  contact. 

The  pressman  who  clamps  the  plates  on  a  modern  lightning  news- 
paper press  does  not  see  anything  very  startling  or  interesting  in  the 
work.  The  man  who  pulls  levers  in  the  pulpit  of  a  great  steelworks 
is  not  apt  to  realise  that  there  has  been  a  marvellous  advance  in  the 
realm  of  manufacture.  The  attendant  on  a  bottle-blowing  machine 
has  learned  to  take  his  work  as  a  matter  of  course.  It  is  found 
through  the  entire  list  of  trades  and  occupations. 

Yet  each  of  these  men  is  at  times  impressed  by  the  remarkable 
advances  made  in  some  industry  other  than  his  own,  because  such 
knowledge  comes  to  him,  as  it  were,  suddenly,  not  by  the  almost 
imperceptible  movement  which  marks  progress  in  work  that  is 
familiar. 

The  means  which  have  brought  about  industrial  development 
are  worth  studying.  No  armed  warrior  ever  sprang  full-grown 
from  his  cradle;  no  giant  industry  has  ever  come  into  being  in  a 
year  or  decade.  It  takes  time  to  develop  the  machinery  and  acquaint 
the  world  with  the  advantages  of  a  new  aid  to  manufacture,  to 
commerce,  to  civilisation,  or  to  human  comfort.  He  who  reads  this 
book  can  hardly  fail  to  be  impressed  with  the  idea  that  no  man 
can  measure  the  possibilities  of  industrial  growth.  Who  can  say 
that  at  the  close  of  the  twentieth  century  "  Darkest  Africa  "  may 
not  be  under- selling  us  in  our  home  markets?  Who  can  be  sure  that 
with  the  development  of  China  and  the  East,  there  may  not  come 
supremacy  in  industry  before  which  our  light  shall  pale  ?  To-day 
the  industry  is  exceptional  in  which  there  has  not  been  an  entire 
alteration  and  renewal  in  the  machinery  within  the  last  few  years. 

The  tale  of  manufacturing  progress  is  one  not  half  told,  one  which 
never  can  be  told  in  full,  because  it  grows  faster  than  the  ability 


489529 


yi  '~\     PREFACE 

^t6*rteora»ite  dev6lo'pmeixi>;  In  every  vocation,  in  every  city  of  the 
globe,  are  geniuses  studying  how  to  advance  the  lines  of  work  in  which 
they  are  engaged.  Every  year  the  standards  that  win  success  are 
set  higher,  yet  every  year  witnesses  increasing  gains  and  greater 
triumphs. 

Electricity  is  believed  to  pervade  the  universe.  Astronomers 
see  evidence  of  its  action  in  the  sun,  in  the  stars,  in  the  comets. 
Its  properties  are  so  varied,  it  affects  substances  so  differently, 
that  it  is  safe  to  say  that  we  have  as  yet  learned  but  a  fraction  of 
what  mankind  is  destined  to  know  about  this  wonderful  thing. 
Because  it  so  readily  lends  itself  to  the  transmission  of  energy,  we 
think  of  it  as  a  source  of  power,  whereas  really  it  is  but  a  means  of 
transmitting  power,  like  the  endless  leather  belts  commonly  used 
for  driving  machinery. 

The  man  who  thinks  he  will  read  up  a  little  on  electricity  is  some- 
times very  much  disappointed  because  he  cannot  learn  at  the  out- 
set, in  a  little  primer,  just  what  electricity  is,  and  so  advance  step 
by  step  to  a  full  knowledge  of  the  subject.  But  there  is  no  help  for 
it.  The  operator  of  electricity  to-day  must  begin,  as  did  those  who 
came  before  him,  at  the  other  end  of  the  problem,  and  learn  how 
electricity  acts  and  what  it  does.  After  a  time  he  will  acquire  a 
notion  of  things  which  will  satisfy  his  craving  for  knowledge,  and 
will  cease  to  bother  much  about  the  theory. 

Operators  and  others  who  follow  the  instructions  in  this  book  will 
soon  be  convinced  of  the  great  importance  of  welding  processes  to 
the  future  manufacturing  and  industrial  world.  It  is  the  simplest 
possible  axiom,  when  we  stop  to  think  (though  few  people  ever  do 
stop  to  think),  that  the  only  way  in  the  long  run  for  labour  as  a 
whole  to  get  more  wealth  is  for  it  to  create  more  wealth ;  the  only 
way  to  create  more  wealth  is  to  increase  productivity  of  labour. 

The  field  for  the  further  application  of  welding  is  enormous; 
but  this  further  application  is  being  delayed  by  lack  of  com- 
plete knowledge  of  the  art,  the  utterly  confusing,  and,  in  many 
cases,  diametrically  opposed  claims  of  competing  interests.  There 
is  needed  a  cultivation  of  the  co-operation  spirit  which  will  permit 
a  frank,  open  discussion  of  the  merits  of  the  different  processes, 
so  that  a  reasonable  agreement  as  to  those  merits  may  be  reached. 
If  there  are  prospective  users  of  welding  who  are  in  doubt  as  to 
whether  they  should  use  gas  or  electric  welding,  or  neither,  can  it  be 
supposed  that  their  confidence  in  any  process  will  be  enhanced  by 
hearing  its  advocates  claim  that  it  is  the  only  safe  and  economical 
one  ?  I  am  not  setting  forth  impracticable  ideals,  but  rather 


PREFACE  vii 

common-sense  principles,  already  found  successful  in  many  business 
fields,  the  application  of  which  is  bound  to  yield  the  best  results 
for  all  concerned. 

It  would  be  difficult  to  suggest  a  branch  of  the  applied  arts  which 
has  advanced  more  rapidly  in  recent  years  than  that  of  electric  and 
oxy-acetylene  welding.  Both  processes  gained  status  in  the  war; 
and,  although  some  of  the  more  extreme  manifestations  of  their 
possibilities  which  the  war  encouraged  are  little  likely  to  be  paralleled 
in  the  early  days  of  peace,  the  methods  have  now  won  for  themselves 
a  definite  place  in  the  shop  routine.  They  have  established  their 
ability  to  tackle  certain  classes  of  work  in  an  economical  and  satis- 
factory way.  That  both  methods  are  destined  to  advance  in  useful- 
ness, alike  in  extension  and  intension,  there  is  no  question;  and, 
although  they  are  in  the  hands  of  specialist  firms,  the  general  shop 
manager  of  the  not  far  distant  future  is  likely  to  find  that  he  is 
expected  to  be  able  to  apply  them.  Moreover,  not  only  the  manager, 
but  others,  both  the  engineers  and  the  "  semi-skilled,"  are  likely  to 
find  interest  and  profit  in  these  processes.  There  is  probably  no 
other  recent  improvement  in  applied  mechanics  which  has  received 
the  scientific  study  devoted  to  autogenous  welding.  The  result  is 
that  its  practice  has  become  an  art  to  which  one  must  give  intelligent 
and  well-directed  study  if  one  would  avail  oneself  of  its  uses. 

The  universal  application  of  this  process,  in  every  branch  of 
industry  where  metals  are  employed,  makes  inevitable  a  great  de- 
mand for  capable  operators.  It  is  to  the  advantage  of  all  concerned 
that  operators  should  understand  their  work  and  their  tools,  that 
they  should  be  able  to  apply  intelligently  the  principles  involved. 


INTRODUCTION 

IN  presenting  this  book  to  the  welding  industry,  I  may  say  that  I 
have  devoted  my  whole  time  to  the  welding  processes  and  the 
materials  used,  and  they  are  all  concisely  described  in  their  various 
chapters.  If  the  readers  will  give  attention  to  the  following  pages, 
they  will  find  many  points  that  will  help  them  in  their  studies  and 
guide  them  to  a  knowledge  of  the  processes.  In  the  course  of 
eighteen  years'  experience  of  the  welding  industry  I  have  found  that 
such  a  book  as  the  present  is  badly  needed.  I  now  make  an  en- 
deavour to  supply  the  deficiency.  It  is  my  desire  to  do  all  in  my 
power  to  raise  the  status  of  welders  in  this  country;  and  this  will 
be  best  achieved  if  they  can  be  induced  to  pursue  a  course  which 
will  make  them  proficient. 

Some  time  ago  an  effort  was  made  to  establish  a  system  of  certifi- 
cates of  proficiency  for  operators,  but  unity  between  the  associa- 
tions interested  is  not  yet  sufficient  to  allow  this. 

In  the  comparatively  limited  space  available  for  my  purpose, 
I  have  attempted  to  give  a  clear  and  consecutive  description  of  the 
principles  upon  which  an  industry  of  unsurpassed  importance  is 
based.  With  the  object  of  accomplishing  my  task,  however,  in  a 
manner  at  once  agreeable  and  instructive,  I  have  now  and  again 
departed  from  the  general  plan  to  dwell  on  some  particular  point. 

While  sensible  of  the  defects  in  my  book,  I  venture  to  hope  that 
to  those  practically  engaged  or  interested  in  the  conduct  of  numerous 
processes  covered  by  its  title  it  may  prove  to  be  of  service. 

I  take  this  opportunity  of  acknowledging  my  gratitude  for 
assistance  from  Messrs.  British  Oxygen  Company,  Ltd.,  Messrs. 
Charles  Bingham  and  Company,  Ltd.,  Messrs.  Leeds  and  Butter- 
field,  Messrs.  British  Insulated  and  Helsby  Cables,  Ltd.,  and  H.  M. 
Hobart,  President  of  the  American  Welding  Society. 


ix 


CONTENTS 


CHAPTER 

PREFACE   -  ... 

INTRODUCTION    -  .        .        -        -  . 

iXl.  WELDING  IN  GENERAL 

Concise  description.     Articles  welded. 

II.    LEAD    BURNING       - 

Description  of  the  gases.     Samples  of  welds. 

III.  MANUFACTURE    OF    OXYGEN 

Describing  Brin  process.    Linde  liquid  air.    Process  described. 

IV.  MANUFACTURE    OF    HYDROGEN 

Description  of  process.     General  details. 

V.    MANUFACTURE    OF    CARBIDE 

History.     Starting-point  of  the  acetylene  industry.     Principal 
materials  for  carbide. 

VI.    ACETYLENE  -  ... 

Physical  properties.     Weight  of  water  to  weight  of  carbide. 
Impurities.    Purifying  materials. 

VII.    OXYGEN    CYLINDERS 

Manufacture  of  cylinders.     Regulations. 

VIII.  ACETYLENE  GENERATORS  - 

General  construction.    Polymerisation.   Working  of  generator 
described.     General  rules. 

IX.    OXYGEN   REGULATORS          -  - 

Description  of  regulator.     Special  coupling. 

X.    REGULATIONS  - 

Regulations  for  generators. 

XI.    BLOWPIPES 

Pattern  and  consumption.     Series  of  blowpipes.     Testing  the 
gases.     General  rules. 

XII.    FLEXIBLE    TUBING  ... 

Quality  of  rubber  tubing. 


PAGES 
V 

ix 
1-5 

6-12 
13-16 
17-21 

22-26 

27-34 

35-39 
40-45 

46-48 
49-51 
52-64 

65-66 


XI 1 


CONTENTS 


CHAPTER 

XIII.  SAFETY    VALVES 

Descriptive  notes.     Choice  of  safety  valve. 

XIV.  PURIFIERS 

Remarks  on  design.  Testing  the  purifier.  The  Keppler  test. 

9 

XV.  SELECTION  AND  INSTALLATION 

Generators  described.  Conditions  a  generator  should  fulfil. 
Order  of  installation. 

""METHODS    OF    WELDING 

Preparations  prior  to  welding.     What  causes  adhesion. 
Test-pieces  for  operators. 


XVII.-PREPARATION 

Bevelling.    Defective  welding  illustrated.    Phenomenon  of 
expansion. 

XVIII.    WELDING   TABLES 

Construction.     Illustration  of  canting  tables. 

XIX.    FURNACES    FOR    HEATING 

Description   of   furnace.      Best   method  of   preheating. 
Expansion  and  contraction. 

XX.    IRON    AND    STEEL 

Difference  between  iron  and  steel.     Physical  properties. 
Pure  iron.     Interposition  of  oxide. 

XXI.    CAST   IRON 

The  strength  and  solidity.    Action  on  cooling.    White  and 
grey  iron.     Difficulties  of  expansion. 

XXII.    DISSOLVED    ACETYLENE 

Brief  description.    Regulations.     Correct  tip  of  flame. 

XXIII.  CUTTING    IRON    AND    STEEL       - 

Illustration  of  cutter.     Oxidation  of  iron  and  steel  under 
oxygen.     Heat  value  of  carbo-hydrogen. 

XXIV.  THERMIT    WELDING       - 

Preparation.   Thermit  required  for  welding.    Composition 
of  thermit. 


PAGES 

67-71 


72-77 
78-82 

83-92 
93-99 

100-103 
104-108 

109-119 
120-131 


154-159 


XXV.    PROPERTIES    OF   PRINCIPAL  NON-FERROUS   METALS 
Important  properties.     Table  of  melting-points. 

XXVI.    DELTA   METALS 
Table  of  metals.     Important  to  operators. 

LXVII.    ALUMINIUM        ..... 

160-163 
164-167 
168-176 

Comparative  cost.     Melting-points  of  the  metal  and  its 
oxide.     Alloy  mixture.     Points  on  welding. 


XXVIII.    COPPER 

Principal  varieties. 
welding. 


177-183 


Special  welding-rods.     Failures   in 


CONTENTS 


Xlll 


CHAPTER 

XXIX. 


BRONZE  .... 

Bronze  welding.     Power  of  the  blowpipe. 


XXX.    BRASS  ...... 

Physical  properties.     Melting-points. 

XXXI.  AMERICAN  METHODS 

Description  of  what  is  being  done.  Welding  machines. 
Medium-pressure  generator.  Cutting  machines.  Non- 
flash  blowpipe. 

XXXII.    THE    METALLURGY    OF    ARC    WELDING 

Metallurgy  of  steel.     Gas-holes  in  electric  welds.     Im 
purities. 


PAGES 

184-186 


187-190 
-191-199 

200-205 


XXXIII.  BRIEF   DESCRIPTION    OF    ELECTRIC    WELDING  -       206-210 

Spot,  butt,  seam  arc  detailed.     Relative  cost.     Rivets 
versus  welds. 

XXXIV.  ELECTRIC   ARC   WELDING         -  -      211-226 

General   processes.     Quasi -arc   process.     Welding  with 
metallic  electrodes.     Practical  notes. 

XXXV.    SPOT    WELDING  -       227-235 

Sheets  to  be  welded.     Articles  that  can  be  spot  welded. 

XXXVI.    ELECTRIC    BUTT    WELDING       -  -       236-243 

Butt- welding  processes.      Electric  current  no  effect  on 
weld.     Chain  welding. 

XXXVII.    ELECTRIC    SEAM    WELDING      -  -       244-246 

Welding  sheet  brass.     Working  operation. 

XXXVIII.    EYE-PROTECTION   IN   IRON    WELDING    OPERATIONS      -       247-257 
Remarks  on  types  of  glass.     Proper  selection  of  colour. 
Summarising. 

XXXIX.    MIRROR   WELDING       -  -       258-263 

Describing  the  process.  Showing  how  mirror  welding  can 
be  accomplished.     Welding  a  boiler. 


LIST   OF  ILLUSTRATIONS 


FIG.  PAGE 

1.  CUTTING    BOILER  FLANGES    AUTOMATICALLY   WITH  A  "  RADIOGRAPH  "  -  5 

2.  INJECTOR   BLOWPIPE            ...  7 

3.  SHOULDER  TAPS   FOR   USE   WITH   LEAD-BURNING   BLOWPIPE           -  7 

4.  OXYGEN   REGULATOR           -                                                                                          .  .  8 

5.  LEAD-BURNED   JOINT           .......  9 

6.  LEAD-BURNED   JOINT            -                 -                 -                 -                 -  -  9 

7.  MOULDING    TOOL   FOR   HEAVY   VERTICAL   WELDING  -  10 

8.  4,000-UNIT  GENERATORS   FOR   PRODUCING   OXYGEN    AND   HYDROGEN  -  20 

9.  SECTION    OF   AN    OXYGEN    CYLINDER             -  39 

10.  10-CWT.    CARBIDE-TO-WATER   GENERATOR                   -                 -  42 

11.  DAVIS  -  BOURNONVILLE       50       POUNDS       CAPACITY       MEDIUM  -  PRESSURE 

GENERATOR          -                                                      .....  43 

12.  DAVIS  -  BOURNONVILLE       100       POUNDS       CAPACITY      MEDIUM-PRESSURE 

GENERATOR          -  44 

13.  OXYGEN  REGULATORS:   1  TWO  GAUGES,   1   ONE  GAUGE,   1  NO  GAUGE  -  46 

14.  DOUBLE    CYLINDER   CONNECTOR    -  -  47 

15.  AIRTIGHT   CARBIDE   CHAMBER,    "  ATOX  "    TYPE       -  -  50 

16.  FOUCHE    BLOWPIPE,    SECTION    AND    ELEVATION      -  52 

17.  UNIVERSAL  TYPE   BLOWPIPE,    HEAD    AT    SPECIAL    ANGLE  -  53 

18.  UNIVERSAL   SINGLE   TYPE    BLOWPIPE           -  -  53 

19.  UNIVERSAL   MULTIPLE   TYPE    BLOWPIPE,    SMALL   SIZE         -  -  54 

20.  UNIVERSAL  MULTIPLE   TYPE  BLOWPIPE,    LARGE    SIZE         -  -  54 

21.  ENDAZZLE   BLOWPIPE,    SINGLE   TIP   PATTERN           -  55 

22.  ENDAZZLE    BLOWPIPE,    MULTIPLE   TIP   PATTERN     -  -  56 

23.  OSBORNE   BLOWPIPES,    FOUR   DIFFERENT   TYPES    -  57 

24.  DAVIS-BOURNONVILLE   SMALL   SET    OF    INTERCHANGEABLE   TIPS-  -  58 

25.  DAVIS-BOURNONVILLE   LARGE    SET    OF   INTERCHANGEABLE   TIPS    -  -  59 

26.  SHOWING   THE    CORRECT   NEUTRAL  FLAME                                                     -  63 

27.  SAFETY   VALVE,    ELEVATION   AND    SECTION  -  68 

28.  STANDARD    SECTIONAL   TYPE    SAFETY    VALVE           -  -  69 

29.  PURIFIER,  SHOWING  SECTION  AND  ELEVATION  WITH  PURIFYING  MATERIAL  74 

30.  "  ATOX  "    PURIFIER               -                                                      -  -  75 

31.  BUTT   JOINT                                -  -  85 

32.  INDENTS,   NOT   SUFFICIENT   WELDING-ROD    ON        -  85 

XV 


xvi  LIST  OF  ILLUSTRATIONS 

««•  PAGE 

33.  BOUND    BAR   BEVEL,    CHISEL   POINTS            -                 -                 -  -                 -  87 

34.  TUBE   BEVEL             .                 1                 ......  87 

35.  FRACTURE   AFTER   BENDING              -                 -                 -                 -  -  88 

36.  LACK    OF   PENETRATION      -                 -                 -                 -                 -  -                 -  88 

37.  SINGLE   BEVELLED   JOINT                                     -                 -                 -  -                 -  89 

38.  ADHESION,    BAD   WELD       -                  -                 -                 -                 -  -                 -  89 

39.  NOT   FULLY    PENETRATED,    FIRST   STARTING   OF   FRACTURE  -                 -  90 

40.  NOT   PENETRATED   THROUGH            -                 -                 -                 -  -                 -  90 

41.  BENDING    A  TEST-PIECE   IN    A   VICE                                                  -  .  91 

42.  FLAT   BAR   DOUBLE    BEVEL                -                 -                 -                 -  -                 -  94 

43.  ANGLE   IRON,    BEVELLED    ONE   SIDE             -                 -                 -  -                 -  94 

44.  NOT   PENETRATED                                                       -                 -                 -  -                 -  95 

45.  SPACE   SHOWN  UN  WELDED                                                  ....  95 

46.  MACHINE    OPERATOR  WELDING   SEAMS    116   INCHES   LONG  -                 -  96 

47.  CASTING    BROKEN,    SET   AND    CRAMPED,   AND   WELDED       -  -  97 

48.  PROPER  SET  FOR  WELDING  PIPES                -                -                -  -  98 

49.  WELDED    CROSS   IN   PIPE                                                          •                 -  -  98 

50.  SHOWING    CONSTRUCTION    OF   PIPE                                                      -  -  98 

51.  SHOWING   PIPE   AT   45   DEGREES,   WELD    AND    BEVEL           -  -  98 

52.  MILD    STEEL   OPERATOR'S   TABLE   -  -  100 

53.  ADJUSTABLE   WELDING   TABLE  WITH   VICE   ATTACHMENT  -  101 

54.  OPERATING   TABLE   WITH  FIRE-BRICKS        -  -  102 

55.  TABLE   FOR   A  NUMBER   OF   OPERATORS      -  -  102 

56.  TILTING    TABLE       -                                    -  -  103 

57.  A   KEROSENE   PREHEATING    TORCH  -  104 

58.  GAS-HEATED    PREHEATING    OVEN  -  -  105 

59.  ASBESTOS    SCREEN   FOR   COVERING    CASTINGS           -  -  106 

60.  LIGHT   LIFTING    CRANE        -  -  107 

61.  TENSION AL   TESTS                                     -  -  117 

62.  CAST-STEEL   TRAMWAY    GEAR   CASE   WELDED            -  -  121 

63.  CAST-IRON   PRESS   SIDE   BROKEN    -  122 

64.  CAST-IRON  PRESS   SIDE  WELDED  122 

65.  TWO- CYLINDER   MOTOR   ENGINE    BROKEN  -  .              -  129 

66.  TWO-CYLINDER  MOTOR   ENGINE   WELDED                                   -  -  130 

67.  BROKEN  WATER  PUMP        -  -  131 

68.  PERFECT   NEUTRAL  FLAME  -  133 

69.  HAND-CUTTING   BLOWPIPE  -  136 

70.  THE    "  RADIOGRAPH  "    CUTTING    STEEL   PLATE         -  -  139 

71.  COUPLED    CYLINDERS,    FOR   CONTINUOUS   WORK    -                 -  -  140 

72.  CUTTING   ROUND   THE   FLANGE    OF   THE   END    OF    A   BOILER  -  141 

73.  CIRCULAR   CUTS   IN   STEEL  PLATES   2J   INCHES   THICK         -  -  142 

74.  CUTTING    A   CAST-STEEL   TURBINE   ROTOR   9   INCHES   THICK  -  144 

75.  FELLING    A   STACK   WITH   AN    OXYGEN    CUTTER        -  146 


LIST  OF  ILLUSTRATIONS 


xvii 


Fin.  PAGE 

76.  THE    lA   OXYGEAPH,    AUTOMATIC   PANTOGRAPH    CUTTING   MACHINE  -  14? 

77.  OXYGBAPH  TRACER  WHEEL,    SWIVEL  STANDARD    -  -  148 

78.  OXYGRAPH   MACHINE    CUTTING   TORCH   WITH  MOTOR   CONTROL   SWITCH     -  149 

79.  SMALL   SOLID    END    CONNECTING-ROD   AND    BILLET  -                 -  150 

80.  LEATHER- CUTTING   PUNCH   FOR   SHOE   MANUFACTURE          -  -  150 

81.  WRENCH  TRIMMING    DIE    ROUGHED   OUT  ON  OXYGRAPH      -  -  151 

82.  VIEWS    OF   THREE    DIES    CUT   FROM    110-POINT    CARBON   STEEL      -  -  152 

83.  NEW   TEETH  PUT   IN   WHEEL   BY    "  THERMIT  "    WELDING  -                 -  154 

84.  THERMIT-WELDED    LOCO   FRAME    -  -  155 

85.  THERMIT-WELDED    ROCK   CRUSHER                                                     -  -                 -  158 

86.  FRACTURED    ALUMINIUM   GEAR   CASE            -  -                 -  171 

87.  FRACTURED    ALUMINIUM -ALLOY    GEAR   CASE  -  175 

88.  ALUMINIUM- ALLOY    GEAR   CASE   REPAIRED  -  176 

89.  SECTION    OF    A    COPPER   WELD  -  179 

90.  MICROPHOTOGRAPHS   FROM   THE   REGION    OF   A   WELD         -  -  182 

91.  THE   DUOGRAPH   WELDING   MACHINE            -  -  192 

92.  SHOWING    DIFFERENT   OPERATIONS    OF   THE    DUOGRAPH     -  -  193 

93.  MEDIUM-PRESSURE    GENERATOR,  200   POUNDS    CAPACITY  -  -  195 

94.  PART    SECTION,    NON-FLASH   BLOWPIPE       -  -  196 

95.  AIR-GAS   PREHEATING   TORCH           -                                                     -  -  197 

96.  WELDING   TORCH   TIP    DIRECTLY    ON   METAL                               .  -  197 

97.  WELDING   TORCH   TIP   DIRECTLY    AGAINST    BRICK                    -  -  198 

98.  DRILLING    A  HOLE   THROUGH   5-INCH   AXLE                                 -  -  199 

99.  SHOWING    AREAS   AT   HIGH   MAGNIFICATION  -  201 

100.  SHOWING   AREAS    AT   HIGH   MAGNIFICATION  -  201 

101.  ELECTROLYTIC  IRON                               -                                                     -  -  202 
02.    ELECTROLYTIC   IRON    NITROGENISED    BY    ANNEALING          -  -  202 

103.  EDGE    OP   WELD   MADE   WITH    COVERED    ELECTRODE            -  -  203 

104.  UNANNEALED   WELD    SECTION         -                                                      -  -  203 

105.  ADHESION   IN   WELD  -  204 

106.  SLAG    ENCLOSED   IN   WELD                                                                       -  -  204 

107.  USE   OF   METAL   ELECTRODE   IN   WELDING    STEEL   BANDS  -  217 

108.  USE    OF    CARBON   ELECTRODE   WITH   METAL  FILLER  -  218 

109.  SEAM   PREPARED   FOR  HAND   WELDING   WITH   CARBON   ELECTRODE  -  219 

110.  COMPLETE  UNIT  FOR  ELECTRIC   ARC  WELDING     -  -  221 

111.  AUXILIARY   PANEL                                                                                          -  -                 -  222 

112.  PRESCOT   SPOT   WELDER     -                                                                        -  -  230 

113.  SPOT-WELD   FLAT   BARS   TO    CORRUGATED    SHEETS                  -  -  231 

114.  PIECE    OF   ANGLE   IRON   TO    FLAT   PLATE    -  -  231 

115.  ROUND   IRON   TO    ANGLE   IRON         -  -  232 

116.  BUTT-WELDING    TOOL   STEEL            -    •  -  239 

117.  FLASH   AND    UPSET   WELD                                     -                 -  -  240 

118.  PRESCOT    BUTT   WELDER    -------  241 


xviii  LIST  OF  ILLUSTRATIONS 

FIG.  I'AGE 

119.  BUTT   WELDER  MAKING    CHAINS     -  -  242 

120.  ELECTRIC   SEAM-WELDING   MACHINE  .  245 

121.  SPECTRUM    OF   A  MAZDA  LAMP       -  .                 .  248 

122.  PFUND   GOLD  GLASS   GOGGLES         -  -                 -  248 

123.  POPULAR  FORM    OF   HELMET   WITH   CIRCULAR   WINDOW     -  -  249 

124.  WELDER'S  HAND  SHIELD  .            .  250 

125.  ALUMINIUM   HELMET,    FRONT    AND    BACK   VIEWS   -  -                 -  251 

126.  SUNDRY    SPECTRA   6  -                 -  252 

127.  SUNDRY    SPECTRA   7  -  253 

128.  FIBRE   GOGGLES     -  -                 -  254 

129.  TWO    PAIRS    OF   GOGGLES   FITTED   WITH   ESSENTIALITE    AMBER   LENSES     -  257 

130.  PRINCIPLE    OF   MIRROR  WELDING  -                 -  259 

131.  MIRROR  WELDING    AS    APPLIED   TO    THE   PIPES       -  -                 -  260 

132.  INTERNAL   WELDING    OF    A   BOILER               ...  .  261 


MODERN 
METHODS    OF    WELDING 


CHAPTER  I 
WELDING  IN  GENERAL 

IT  is  well  known  to  everyone  who  takes  an  interest  in  welding  and 
welding  processes  that  the  existing  opinion  as  to  the  value  of  the 
processes  and  the  practical  results  obtained  is  in  a  state  of  uncer- 
tainty. The  chief  ground  for  this  uncertainty  lies  in  the  fact  that 
these  new  processes  have  only  been  introduced  recently  into  indus- 
trial practice,  and  rest  entirely  on  an  empirical  basis.  Although 
oxy- acetylene  welding  is  now  extensively  used,  and  is  of  great 
theoretical  and  practical  interest,  it  has  never  been  made  the  object*^ 
of  systematic  and  exhaustive  research. 

The  author  has  had  eighteen  years'  experience  of  welding,  and  has 
made  exhaustive  tests  and  long  studies,  not  only  of  what  is  being 
done  in  this  country,  but  also  of  the  progress  made  in  the  United 
States  and  Germany.  The  latter  country  is  far  more  advanced 
than  Great  Britain.  The  Germans  have  carried  out  systematic  ^ 
and  exhaustive  researches.  Their  operators  are  scientifically 
trained,  are  taught  metallurgy  and  chemistry,  including  the  chemi- 
cal compositions  and  melting-points  of  all  metals  and  oxides,  make 
test-pieces  for  experimenting  with  the  chemical  and  mechanical 
tests,  and  employ  microscopic  and  macroscopic  examinations,  both 
of  the  melted  zone  and  the  neighbouring  parts.  Their  welding,  as 
a  rule,  is  very  neat,  as  they  are  not  allowed  to  execute  commercial 
work  until  they  have  become  fully  proficient. 

The  introduction  of  oxy- acetylene  welding  has  opened  up  an 
enormous  field,  in  which  any  metal  can  be  dealt  with,  and  such  an 
article  as  a  cracked  motor  frame  or  cylinder  can  be  rapidly  welded. 
In  these  directions  there  seems  to  be  ample  scope  for  the  applica- 
tion of  engineering  skill,  and  recent  developments  have  shown  that 
it  is  difficult  to  put  a  limit  to  the  purpose  to  which  engineers  may 
yet  apply  the  process. 

To-day  the  business  has  grown  beyond  the  limits  of  personal 
supervision.  The  necessity  for  organised  instruction  of  operators 
is  becoming  more  and  more  obvious  in  the  interest  of  both  work- 

1 


2  MODERN  jMET&CKDS  OF  WELDING 

men  and  employ  CE/<  Secv<aral  gelding;  schools  have  now  been  started 
in  various  cenfreVabdut  the* '^duritry,  whence  a  stream  of  qualified 
welders  is  already  beginning  to  flow  to  the  workshops,  where  most 
of  them  are  able  to  turn  their  training  to  practical  use. 

They  teach  the  operator  under  practical  conditions  the  right 
flame  for  different  work,  the  principles  on  which  the  blowpipe  is 
constructed,  the  way  to  handle  it,  and  a  variety  of  technical 
and  theoretical  points,  which  are  always  useful  to  him  in  his  sub- 
sequent career.  He  is  also  taught  thoroughly  the  construction, 
working,  and  maintenance  of  the  plant. 

It  is  the  operator  of  to-day,  well  instructed  in  the  points,  whom 
we  hope  to  find  the  professional  welder  of  to-morrow.  The  time 
is  not  far  off  when  employers  will  refuse  to  engage  a  welder  unless 
he  can  produce  the  certificate  of  proficiency.  This  cannot  be 
obtained  unless  the  operator  possesses  thorough  knowledge  and 
practical  experience  of  the  process. 

The  author  has  undertaken  many  investigations  in  this  process. 
The  oxy-acetylene  method,  when  properly  worked,  possesses 
numerous  marked  advantages.  In  the  first  place,  the  operating 
flame  can  easily  be  controlled,  and  the  temperature  attained  at 
various  zones  can  be  readily  regulated.  Secondly,  the  work  can 
be  easily  accomplished,  owing  to  the  high  temperatures  reached 
(3,600°  C.),  and  the  appliances  are  convenient  to  handle  and  reliable 
in  operation. 

The  most  important  conditions  for  securing  good  results  are — 
V\*  The  use  of  the  purest  acetylene  possible. 
^2.  The  use  of  a  blowpipe   so  designed  as  to  ensure  accurate 
adjustment  in  the  proportion  of  the  mixed  gases  and  to  secure  their 
exit  at  a  velocity  capable  of  keeping  the  metal  sufficiently  fluid 
without  the  melting  flame  being  too  rigid. 
f'3.  The  use  of  an  absolutely  pure  welding-rod. 
l/  4.  The  provision  of  an  absolute  neutral  zone  in  the  melting  flame, 
neither  oxidising  nor  reducing. 

^  5.  The  edges  must  be  free  from   all  impurities,  and,   if  over 
T\  inch  thick,  must  be  bevelled. 

6.  The  use  of  deoxidising  agents  eliminating  the  oxides,  in  view 
of  unavoidable  oxidation  of  the  metal  subject  to  the  melting  process. 
It  is  necessary  to  bear  in  mind  the  relation  between  the  melting- 
points  of  the  oxides  and  of  the  metal  itself,  which  is  a  most  important 
matter. 

4/7.  Rapidity  in  melting,   in  order  to   avoid  excessive  heating, 
which  not  only  alters  and  deteriorates  the   original  structure  of 


WELDING  IN  GENERAL  3 

the  metal,  but  would  even  favour  the  occlusion  of  the  gases  (particu- 
larly hydrogen)  and  so  occasion  the  formation  of  blowholes  in  the 
melted  zone. 

In  addition  to  these  considerations,  care  should  be  taken  that 
no  sudden  cooling  occurs.  The  conditions  may  have  to  be  modified 
on  account  of  the  conductivity  and  special  dilation  of  the  material, 
as  well  as  in  relation  to  the  thickness,  size,  and  shape  of  pieces 
operated  upon. 

For  those  who  are  familiar  with  this  process  of  welding  and  cut- 
ting it  is  not  difficult  to  appreciate  its  varied  applications.  The 
ease  and  rapidity  with  which  experienced  welders  can  carry  out 
repairs  in  situ,  and  the  portability  of  the  plants,  make  the  process 
valuable,  if  not  indispensable.  The  service  rendered  by  it  in  many 
workshops,  where  the  welding  of  articles  of  all  kinds  is  a  daily 
necessity,  is  calculable. 

/The  oxy-acetylene  process  occupies  a  leading  place  in  all  aero- 
plane and  airship  industries.  It  is  used  with  advantage  in  welding- 
sheet  steel  stampings,  cylinders,  aluminium  crank  cases  and 
machinery  parts,  steel  tub^s,  stamped  steel  water-jackets  for  cylin- 
ders, broken  cast  iron.  /Moreover,  for  cutting  iron  and  steel  this 
process  has  no  rival  whatever.  It  will  cut  wrought  iron  or  steel 
plate  20  inches  thick./The  flame  has  been  applied  to  the  case- 
hardening  of  steel,  and  some  firms  are  using  this  on  a  large  scale. 
It  is  well  known  that  the  flame  containing  an  excess  of  acetylene 
is  a  very  energetic  carboniser. 

This  process  may  be  employed  on  any  class  of  work.  It  will  weld 
30-gauge  steel  or  1  J-inch  boiler  plates, /cut  mild  steel  up  to  20  inches 
thick  •!  weld  any  commercial  metal,  such  as  cast  iron,  aluminium, 
copper,  bronze,  zinc,  lead,  delta  metal.  In  the  repair  of  broken 
machinery  and  parts  it  is  always  above  its  rivals;  repairs  are  exe- 
cuted quickly  and  can  be  done  without  dismantling  in  many  cases. 
It  can  be  used  in  the  manufacture  of  safes  and  tanks,  in  the  jointing 
of  pipes,  steam  superheaters,  casks,  artistic  ironwork,  in  adding 
metal  to  parts  worn  by  friction,  filling  up  holes  or  parts  of  new 
structure  cut  away  in  error,  welding  of  tool  steel  to  wrought- 
iron  bars,  and  welding  of  copper  or  brass  tubes.  The  flame  can  be 
used  for  preheating  and  for  hammering  and  annealing  after  welding, 
thereby  ensuring  a  soft  metal,  a  method  not  practicable  in  the  electric 
process. 

In  the  welding  of  light  sheet  steels  with  24-gauge  metal,  45  feet 
per  hour  can  be  welded,  with  a  consumption  of  only  4  feet  of  oxygen 
and  3  feet  of  acetylene.  On  the  other  hand,  when  the  metal  reaches 


4  MODERN  METHODS  OF  WELDING 

|  inch  thick,  electric  welding  has  the  advantage  both  in  speed  and 
cost. 

When  the  process  of  acetylene  welding  was  first  introduced,  its 
apparent  simplicity  led  many  engineers  wrongly  to  assume  that 
welding  appliances  might  be  regarded  as  general  workshop  tools, 
which  any  inexperienced  but  handy  man  could  operate  with  success. 
Consequently  much  work  was  condemned  wholesale  because  of  the 
defects  in  the  weld.  The  author  would  emphasise  that  this  is  not 
the  fault  of  the  process,  but  of  inefficient  workmen. 

It  is  estimated  that  there  were,  during  the  recent  war,  33,000 
employed  in  this  country  in  welding  processes,  of  whom  25,000 
entered  the  field  during  the  war.  Of  the  total  number,  90  per  cent, 
are  not  fully  skilled — that  is,  they  are  incapable  of  executing  satis- 
factory welds  on  all  metals,  being  mostly  employed  oil  sheet  steel. 
The  impetus  that  has  been  given  under  war  conditions  should  stimu- 
late employers  to  investigate  and  exploit  this  revolutionary  process, 
the  possibilities  of  which  have  no  obvious  limits. 

In  the  shipbuilding  trade  this  process  can  be  utilised  very  much 
more  than  at  present — for  instance,  in  making  knee  brackets, 
stays,  and  frames.  These  can  all  be  cut  and  welded  by  blowpipes, 
with  present  costs  reduced  50  per  cent,  and  output  increased. 
A  blowpipe  only  requires  one  man ;  but  an  anglesmith,  when  welding 
a  knee  bracket,  requires  two  or  three  assistants.  Most  shipyards 
have  plants,  but  they  are  not  utilised  to  advantage. 

In  all  welding  it  is  most  important  that  the  work  should  be  ade- 
quately prepared  before  commencing  to  weld,  as  all  time  spent  in 
this  way  is  amply  repaid  afterwards  in  the  easier  execution,  and 
also  by  the  homogeneous  nature  of  the  weld.  It  is,  however,  a 
subject  on  which  it  is  impossible  to  lay  down  any  hard-and-fast 
rules,  the  varying  nature  of  the  work  accomplished  making  it  im- 
possible to  do  so.  The  general  principles  obtained  in  the  best  prac- 
tice point  out  that  the  line  of  weld  must  be  opened  out — that  is, 
the  two  edges  must  be  bevelled  to  an  angle  of  45  degrees,  to  make 
certain  that  the  weld  is  well  penetrated,  not  merely  sealed  over,  and 
to  strengthen  the  weld  by  increasing  the  surface  of  contact. 

One  of  the  most  important  things  to  do  in  the  preparation  is  to 
arrange  the  pieces  to  be  welded  in  such  a  position  that  there  shall 
be  no  deformation,  breaks,  or  cracks,  or  internal  strains,  and  that 
they  may  be  linable  at  the  conclusion  of  the  operation.  This  is  a 
point  in  which  the  skill  and  experience  of  the  operator  are  revealed, 
as  there  are  no  rules  to  guide  him,  and  upon  any  work  but  that  of 
the  simplest  character  failure  to  grasp  and  apply  the  laws  of  expan- 


WELDING  IN  GENERAL  5 

sion  and  contraction  means  the  partial  or  total  ruin  of  the  work. 
It  is  impossible  to  control  expansion  and  contraction  by  physical 
force,  so  the  only  way  to  prevent  disastrous  results  is  to  foresee 
the  probable  direction  and  extent  of  the  phenomena,  and  nullify 
'the  effects  by  preheating  certain  parts  of  the  work,  either  by  the 
blowpipe  or  the  welder's  furnace. 

It  is  good  practice  to  raise  the  temperature  to  nearly  red  heat 
in  the  furnace  and  weld,  then  allow  to  cool  slowly  and  uniformly 


FIG.  1. — THE  RADIOGRAPH,  USED  FOR  CIRCULAR  CUTTING,  AUTOMATICALLY,  AS 
SHOWN,  is  CUTTING  ANNULAR  RINGS  31  INCHES  DIAMETER  BY  6  INCHES 
THICK  AT  A  SPEED  OF  7  INCHES  PER  MINUTED 

Note  the  clean  cut  and  accuracy  of  the  rings. 

in  sand  or  asbestos;  but  all  cold  currents  of  air  must  be  avoided. 
All  castings  should  be  preheated  bodily.  This  is  a  great  advantage, 
for  not  only  does  it  save  gases,  but  it  prevents  any  irregular  expan- 
siorf,  and  hence  no  fractures. 

/  The  cutting  of  iron  and  steel  by  the  oxy-acetylene  flame  is  being 
very  extensively  used.  This  involves  the  use  of  a  blowpipe  of  a 
different  design,  which  provides  for  the  oxy-acetylene  flame  and  an 
auxiliary  jet  of  pure  oxygen  to  be  impinged  on  the  line  of  cutting. 
The  principle  underlying  this  method  consists  of  taking  advantage 
of  the  fact  that,  when  heated,  iron  and  steel  can  be  oxidised  very 
quickly  by  a  jet  of  oxygen,  which  jet,  delivered  at  high  pressure, 
blows  away  the  oxide  that  is  made,  leaving  a  narrow,  clear  cut,  / 
almost  as  clean  as  a  saw  cut. 


CHAPTER  II 
LEAD  BURNING 

THIS  process  is  one  of  fusion  of  lead  by  oxy  hydrogen,  air  hycrogen, 
or  coal-gas  hydrogen.  The  air-hydrogen  process,  dating  back  over 
one  hundred  years,  for  a  considerable  time  was  only  employed  in 
chemical  work  on  the  construction  of  acid  tanks  and  vessels  with 
their  pipe  connections.  The  tanks  being  built  of  wood,  lined  with 
sheet  lead,  the  junction  of  the  sheet  was  effected  by  this  method. 
At  a  later  period  this  system  was  employed  in  large  gasworks, 
more  recently  for  the  manufacture  of  electric  batteries  and  their 
plate  connections.  If  solder  had  been  used  on  either  class  of  work, 
it  would  have  been  attacked  by  the  acid.  It  was  restricted  on 
account  of  its  cost. 

In  the  latter  part  of  the  year  1888  a  series  of  experiments  was 
carried  out  by  the  Erin's  (now  British)  Oxygen  Company,  with  the 
object  of  using  coal-gas  from  the  ordinary  town  main  and  oxygen 
from  a  trade  cylinder.  After  due  consideration  of  the  matter,  it- 
was  thought  possible  to  utilise  the  pressure  of  the  oxygen  cylinder 
to  obtain  an  injection  action  by  which  the  supply  of  coal-gas  at  low 
or  main  pressure  could  be  increased  and  thoroughly  mixed  with  the 
oxygen  in  the  blowpipe  previous  to  ignition.  In  order  to  complete 
combustion  (thus  preventing  the  formation  of  carbon  deposits  on 
the  melted  lead),  after  various  trials  had  been  made,  the  injector 
blowpipe  which  we  illustrate  on  p.  7  was  designed,  and  was  found 
eminently  adapted  to  the  purpose.  It  fulfilled  in  other  respects 
all  the  requirements  necessary  to  ensure  good  work,  and,  moreover, 
as  it  produced  a  flame  at  much  higher  temperature  than  could  be 
secured  by  the  old  hydrogen-and-air  system,  it  enabled  the  plumber 
to  execute  about  double  the  amount  of  work,  of  better  quality,  and 
without  assistance. 

H  (Fig.  2)  is  the  inlet  for  the  coal-gas  supply;  0  shows  the  injector 
inlet  for  the  oxygen  supply,  fixed  in  position  with  the  injector 
removed,  showing  the  coned  end  which  projects  through  the  chamber 
into  a  cone  formed  in  the  body.  The  pipe  leading  away  from  the  body 
is  screwed  at  the  end  to  take  the  nipple,  which  is  of  various  sizes,  to 

6 


LEAD  BURNING  7 

deal  with  lead  from  the  thinnest  section  up  to  J  inch  thick.  The 
essential  features  of  this  type  of  blowpipe  are  the  shape  and  design 
of  the  injector  cones,  with  their  relative  position  to  each  other;  the 
reservoir  for  the  coal  supply  provided  between  the  two  gas  inlets  0 


FIG.  2. — INJECTOR  BLOWPIPE. 

and  // ;  together  with  the  mixing  chamber,  into  which  the  brass  pipe 
is  screwed.  The  flame  also  differs  somewhat  from  that  of  the  old 
hydrogen  type  of  blowpipe,  its  chief  characteristic  being  a  well- 
defined  pale  blue  cone  about  a  quarter  of  an  inch  long.  The  hottest 


jrIG.  3. — SHOULDER  TAPS  FOR  USE  WITH  LEAD-BURNING  BLOWPIPE. 

part  is  the  point  of  the  cone,  which,  in  use,  impinges  on  the  metal 
operated  upon.  Melting  is  clean  and  bright.  This  flame  is  best 
controlled  by  the  use  of  what  are  known  as  "  shoulder  taps,"  illus- 
trated herewith. 

These  taps  in  Fig.  3,  marked  H  and  O  respectively,  correspond 


8  MODERN  METHODS  OF  WELDING 

with  those  on  the  blowpipe,  and  are  connected  by  two  lengths  of 
rubber  tubing,  with  the  twofold  object  of  securing  flexibility  and 
lightness,  the  pressure  being  previously  reduced  from  the  other 
end  of  the  tap,  marked  H.  A  rubber  tubing  leads  to  the  ordinary 
coal-gas  supply  from  the  main,  and  the  oxygen  tap,  marked  O,  is 
similarly  connected  by  a  rubber  tube  with  the  outlet  of  an 
endurance  regulator,  which  is  illustrated  herewith. 

This  regulator  in  Fig.  4  is  connected  by  a  ring  nut,  seen  at  the 
bottom,  to  the  oxygen  cylinder.  The  knurled  nut  on  the  right  is 
screwed  into  the  diaphragm  plate,  indented  on  the  sleeve,  by  which 
means  it  can  be  adjusted  to  maintain  any  constant  outflow  of  oxygen 


FIG.  4. — OXYGEN  REGULATOR. 

from  the  cylinder  up  to  30  pounds  pressure  per  square  inch.  The 
projection  immediately  opposite  is  a  safety  valve,  the  outlet  or  stop 
valve  being  shown  on  top.  These  illustrations  constitute  a  com- 
plete lead-burning  outfit,  with  the  exception  of  the  rubber  tubing 
and  the  oxygen  cylinder.  A  sample  injector  blowpipe  was  submitted 
to  the  Gas  Light  and  Coke  Company  for  trial  in  their  chemical 
works  at  Beckton,  and  gave  satisfactory  results.  A  large  order 
was  consequently  placed.  The  system  has  met  with  universal 
approval,  not  only  in  the  trades  already  mentioned,  but  also  for 
roof  work  and  general  plumbing.  If  lead  burning  is  required  where 
there  is  no  coal-gas  supply,  this  can  be  obtained  compressed  in 
cylinders  similar  to  those  used  for  oxygen ;  but  an  endurance  regula- 
tor would  have  to  be  used  on  the  coal-gas  cylinder.  In  lead  burn- 
ing, in  order  to  secure  sound  joints  in  any  class  of  work,  it  is  neces- 
sary that  the  joints  are  scraped  perfectly  clean  and  bright,  and  also 
the  strip  of  lead  that  is  used  for  filling  in  the  case  of  a  butt  joint. 


LEAD  BURNING  9 

For  lap  joints  no  filling  strip  is  necessary.  In  the  latter  case,  how- 
ever, it  is  equally  important  to  scrape  clean  all  surfaces  to  be  welded, 
including  both  the  overlapping  edges,  otherwise  it  is  not  possible 
to  do  sound  work.  The  illustrations  represent  the  best  methods  of 
executing  the  various  types  of  sheet-lead  burning.  A  (Fig.  5)  is  a  butt 


FIGS.  5  AND  6. — LEAD-BURNED  JOINTS. 

A,  butt  joint;  B,  vertical  joint;  C,  vertical  lap  joint;  D,  lapped  joint  with 
metal  added. 

joint.  Where  added  metal  is  required,  the  line  of  weld  should  be 
about  |  inch  to  f  inch  wide,  and  thickened  up.  This  is  a  very  strong 
joint,  p  is  a  vertical  joint,  which  is  lapped,  and  no  additional 
metal  is  needed.  This  vertical  welding  is  not  as  easy  as  the  butt. 
The  metal  when  molten  falls  very  quickly,  and  unless  the  welder 
is  sharp  the  molten  metal  runs  right  down  instead  of  in  the 


10  MODERN  METHODS  OF  WELDING 

line  of  the  joint.  Much  practice  is  necessary  for  this  type  of 
welding.  C  (Fig.  6)  is  a  vertical  lap  joint,  too.  The  same 
methods  have  to  be  adopted  as  with  type  B.  This  weld  is  not 
so  good  as  type  B,  nor  so  neat.  D  is  a  lapped  joint  with  added 
metal,  the  weld  being  about  f  inch  to  f  inch  wide.  This  is  welded 
horizontally. 

In  chemical  works  very  often  the  sheet  lead  used  is  20  to  30 
pounds,  and  when  vertical  jointing  has  to  be  done  with  this  thick- 
ness it  is  usual  to  employ  what  is  known  as  a  moulding  tool,  which 
is  held  over  the  lap.  The  lead  is  melted  and  allowed  to  fall  into  this 
moulding  tool.  As  soon  as  it  is  cooled,  it  is  pushed  up  a  bit  farther, 
melted,  and  filled  again,  the  operation  being  repeated  until  the  joint 
line  is  finished.  This  moulding  tool  is  simply  a  forged  tool  shaped 
half-round  on  the  inside,  where  it  fits  against  the  lead  joint;  the 
size  is  about  1  inch  by  |  inch  semicircular,  about  J  inch  thick,  with 
a  handle  at  the  other  end.  Below  is  an  illustration  of  one. 


FIG.  7. — MOULDING  TOOL  FOR  HEAVY  VERTICAL  WELDING. 

Lead  burning,  so  called,  is  the  autogenous  welding  of  lead  with 
a  gas  torch.  The  edges  of  the  lead  parts  are  fused  together,  using 
no  solder  or  other  metal  except  pure  lead  to  fill  the  joint.  The  term 
"lead  burning  "  is  really  a  misnomer,  as  metal  is  not  burnt,  but 
simply  fused  and  flowed  together.  This  process  only  is  employed 
for  applying  lead  linings  of  acid  tanks  used  in  chemical  plants, 
fertiliser  factories,  rubber  reclaiming  works,  electroplating  shops, 
nitroglycerine  huts,  and  other  industries.  The  widespread  use  of 
storage-battery  starting  systems  on  motor-cars  has  created  a  demand 
in  garages  and  battery  stations  for  lead-welding  equipment  for  the 
welding  of  lead  connectors  and  terminals. 

Lead  welding  is  used  to  some  extent  in  making  up  pipe  con- 
nections; but  tank  and  storage  work  are  the  chief  applications  for 
which  lead-burning  equipments  are  purchased.  Considerable  skill 
is  required  of  a  lead  burner  to  weld  lead  sheets  together  without 
burning  holes  through  or  causing  the  lead  to  drop.  But  the  trade 
is  one  quickly  learned  by  an  intelligent  workman.  Success  depends 
on  clean,  thorough  preparation,  suitable  equipment,  right  material 
and  right  working  conditions,  as  well  as  personal  skill.  Two  forms 
of  joints  are  used,  the  butt  and  the  single-lap  seams.  The  latter  are 


LEAD  BURNING  11 

used  almost  exclusively  in  tank  burning.  Butt  joints  are  used 
mostly  in  lead-pipe  jointing. 

When  making  a  butt  joint,  the  edges  of  the  sheets  or  pipes  should 
be  trimmed  straight.  They  may  be  rasped  to  75  to  80  degrees  in 
opposite  ways,  so  that  when  the  two  sheets  are  laid  together,  a 
V  groove  of  30  degrees  or  slightly  less  angle  is  formed.  If  a  filler 
is  to  be  used,  the  groove  is  filled  with  molten  lead,  flush  or  slightly 
above  the  surface  of  the  sheets  or  pipes.  A  preparation  of  the  butt 
joint  by  bevelling  is  practised  for  sheet  burning  except  on  very  heavy 
lead — so  thick,  that  is  to  say,  that  it  is  rarely  used.  All  thicknesses 
up  to,  say,  20  pounds  to  the  square  foot  are  butted  with  square  edges 
and  generally  burned  together  without  using  the  filler  rod.  The 
use  of  the  latter  slows  down  the  work,  on  account  of  the  necessity 
of  frequently  cleaning  off  the  oxide  film  on  the  rod.  A  joint  made 
without  the  filler  rod  is  slightly  thinner  than  the  sheet;  but  this  is 
rarely  objectionable.  When  burning  a  butt  joint  with  the  filler 
rod,  the  flame  is  played  on  the  sheets  until  the  metal  is  softened 
to  fusing-point,  but  is  still  too  stiff  to  flow  freely.  The  added  metal 
is  supplied  from  the  lead  filler  rod  to  fill  the  V,  if  prepared  for  a 
groove.  The  filling  rod  is  held  in  the  left  hand  close  to  the  joint, 
so  that  the  heat  of  the  flame  melts  it  and  deposits  molten  lead  into 
the  joint,  alternately  heating  the  sheets  and  the  filler  rod  to  the 
fusing-point,  letting  a  drop  fall  into  place,  then  whipping  the  torch 
off  momentarily  to  allow  the  fused  metal  to  cool.  This  practice 
is  slow  and  seldom  necessary. 

It  should  be  borne  in  mind  that  tank  linings  are  made  of  chemical 
lead — that  is,  new  lead,  free  from  impurities.  Ordinary  sheet  lead 
used  for  gutters  and  other  purposes  is  often  made  of  old  lead,  and 
should  not  be  used  for  acid  tank  linings  which  must  be  autogenously 
welded.  Lap  seams  are  always  used  in  tank  linings  where  a  smooth 
surface  is  not  absolutely  required.  In  making  a  lap  seam  the  top 
sheet  should  lap  over  the  under  sheet  about  |  inch  to  f  inch.  All 
dirt  and  oxide  should  be  removed  carefully  from  the  joint  with  a 
sharp  scraper.  Some  lead  burners  prepare  for  welding  by  painting 
a  strip  of  asphaltum  along  the  edge  about  1  inch  wide,  letting  it 
dry,  and  then  scraping  it  off  about  J  inch  width  next  to  the  edge  with 
a  sharp  scraper,  which  removes  the  oxide  and  the  asphaltum.  The 
asphaltum  tends  to  hold  from  breaking  down  when  overheated,  and 
thus  favours  the  use  of  a  large  flame  burning  at  a  fast  rate.  The 
flame  is  directed  against  the  top  sheet  about  J  inch  from  the  edge. 
Some  burners  give  the  torch  a  circular  motion,  the  diameter  of  the 
circular  path  being  from  J  inch  to  f  inch;  but  the  most  rapid  work 


12  MODERN  METHODS  OF  WELDING 

on  level  seams  is  done  with  no  movement  except  forward.  The 
top  sheet  fuses  and  unites  with  the  metal  beneath,  the  edge  breaks 
down,  and  the  corner  is  filled  with  molten  lead,  which  adheres  to 
the  lower  sheet,  making  a  weld  about  f  inch  wide.  The  burner 
dispenses  with  the  use  of  the  lead  filler  rod  or  solder  stick  on  lap 
seams,  simply  melting  down  the  edge  of  the  overlapping  sheet, 
causing  it  to  unite  with  the  one  beneath. 

In  vertical  lap  seams  the  torch  is  generally  given  an  in-and-out 
motion,  thus  taking  the  flame  close  to  the  lead  and  then  away. 
When  the  flame  is  close  to  the  lead  a  small  section  of  the  upper  sheet 
over  the  seam  melts,  and  slides  down  about  J  inch,  where  it  cools 
and  unites.  The  repetition  of  the  torch  movement  causes  this 
action  to  be  repeated,  drops  of  molten  lead  sliding  down  the  joint, 
uniting  each  time  the  torch  is  held  close.  This  method  is  used  only 
on  vertical  work,  where  it  is  not  feasible  to  do  straightaway  burn- 
ing. Some  welders  give  the  circular  motion  instead  of  the  in-and-out, 
but  the  result  is  practically  the  same. 

The  temperature  needed  for  lead  burning  is  low  in  comparison 
with  that  required  for  welding  cast  iron  or  steel,  being  only  62°  F. 
A  special  torch  is  employed,  which  is  held  in  the  hand  and  manipu- 
lated somewhat  the  same  as  a  soldering  iron.  These  torches  may 
be  used  with  acetylene  successfully. 

The  lead  burner  necessarily  becomes  an  expert  at  working  lead 
within  narrow  temperature  ranges.  He  must  heat  the  metal  at  the 
joint  to  the  fusing-point,  but  not  so  much  that  it  becomes  liquid 
and  drops  away.  When  butt  welding  with  the  solder  stick,  he  must 
avoid  heating  and  adding  metal  so  hot  that  when  it  drops  into  the 
joint  it  burns  a  hole  through  instead  of  filling  the  groove.  He  should 
make  provision  for  growth  or  expansion  of  the  linings  of  the  hot 
tanks.  Repeated  heating  and  cooling  cause  the  lead  to  expand. 
After  a  period  of  use  the  lining  will  be  found  in  a  corrugated  condi- 
tion, due  to  permanent  expansion. 

Lead  burning  of  storage-battery  connections  is  comparatively 
easy,  and  is  quickly  mastered  by  anyone  having  some  mechanical 
skill.  Handy  men  soon  become  sufficiently  expert  in  this  class  of 
work  to  burn  storage-battery  terminals  successfully.  The  danger 
to  be  avoided  is  overheating.  The  operator  must  learn  to  clean 
thoroughly  the  parts  to  be  united,  and  to  apply  the  flame  no  longer 
than  is  required  to  fuse  the  metal  and  bring  about  union.  When 
the  connections  have  been  flowed  together,  the  excess  metal  should 
be  wiped  off  with  a  woollen  cloth  greased  with  mutton-fat  or  beef- 
tallow. 


CHAPTER  III 
JV1ANUFACTURE  OF  OXYGEN 

OXYGEN  is  invariably  the  principal  ingredient  or  combustion  agent 
used  in  the  cutting  of  iron  and  steel  in  autogenous  welding  with  the 
blowpipe.  It  is  necessary  that  those  handling  the  blowpipe  be 
familiar  with  its  properties,  manufacture,  storage,  and  methods  of 
use.  Oxygen  is  the  most  widely  distributed  of  all  bodies.  It 
exists  in  a  state  of  mixture  in  the  air,  which  contains  one-fifth  of  its 
volume  of  this  gas.  Water  is  a  compound  of  oxygen  and  hydrogen. 
It  is  a  colourless,  tasteless,  and  odourless  gas.  One  litre  of  oxygen 
at  0°  C.  and  atmospheric  pressure  weighs  1 43  grammes,  its  density 
is  1-1056,  its  chemical  symbol  0,  its  atomic  weight  16.  The 
characteristic  property  of  oxygen  is  its  power  of  supporting  com- 
bustion ;  a  glowing  candle  will  instantly  burst  into  flame  if  plunged 
in  a  jar  of  oxygen. 

Iron  heated  to  redness  burns  readily  in  air  or  oxygen.  This 
unique  phenomena  is  the  whole  secret  of  the  cutting  of  iron  and  steel 
with  a  jet  of  oxygen  (which  will  be  described  under  "  Cutting  Iron 
and  Steel"  in  a  later  chapter).  The  combustion  is  a  chemical 
reaction  between  the  oxygen  and  the  body  which  burns  with  it. 
The  product  of  the  combustion  is  called  "  oxide." 

The  manufacture  of  oxygen  can  be  carried  out  by  several  pro- 
cesses, some  of  which  are  the  barium  oxide,  the  electrolysis  of  water, 
and  the  Linde  process  of  the  fractional  distillation  of  liquid  air, 
which  brings  about  the  production  of  pure  oxygen.  In  1886,  on 
the  present  site  of  the  British  Oxygen  Company's  works  in  West- 
minster, a  large  oxygen  plant  was  erected,  which  must  take  a  lead- 
ing position  in  any  article  dealing  with  industrial  gases.  The  plant 
was  installed  by  Brin's  (now  the  British)  Oxygen  Company. 
Although  in  itself  a  qualified  success,  it  led  to  the  development  by 
that  Company  of  a  process  which  was  destined  to  supersede  all  other 
known  methods  of  manufacturing  oxygen,  and  greatly  to  enhance 
the  commercial  value  of  the  gas. 

The  Brin  process  of  producing  oxygen  is  based  on  the  barium- 
oxide  process,  first  suggested  by  the  eminent  chemist  Boussingault 
in  1857.  Boussingault  discovered  that  at  a  temperature  of  about 

13 


14  MODERN  METHODS  OF  WELDING 

1,000°  F.  the  monoxide  of  the  metal  barium  would  absorb  oxygen 
readily  from  the  atmosphere,  with  the  resulting  formation  of  the 
dioxide,  and  that  at  a  higher  temperature  of  about  1,600°  F.  the 
oxygen  thus  absorbed  would  be  given  off  again,  and  monoxide 
restored  to  its  original  condition,  ready  for  the  cycle  to  be  repeated. 
Continuous  efforts  were  made  to  establish  a  commercial  process  for 
the  production  of  oxygen  on  this  apparently  indestructible  reaction 
of  barium  oxide.  In  spite,  however,  of  its  chemical  simplicity, 
many  practical  difficulties  arose,  which  remained  unsurmounted 
until  the  event  of  the  Brin's  Oxygen  Company  in  1886.  The  Com- 
pany was  formed  to  work  the  patents  of  the  two  French  chemists 
whose  names  it  bore.  Initial  experiments,  conducted  on  a  small 
scale  under  these  patents,  had  met  with  considerable  success,  so  that 
a  large  plant  was  laid. 

It  will,  however,  be  seen  from  what  has  already  been  stated  that 
the  Company's  old  title  was  always  somewhat  of  a  misnomer.  The 
process  which  has  made  them  not  only  the  oldest  and  leading  gas 
compressors  of  the  day,  but  also  the  pioneers  of  the  gas  cylinder  in- 
dustry, has  always  been  more  British  than  Brin.  Although  now  only 
of  historical  interest,  the  barium  process  is  entitled  to  more  than  a 
passing  recognition  in  any  description  of  the  development  of  industrial 
oxygen,  because  the  industry  was  not  only  founded,  but  was  success- 
fully conducted  by  means  of  that  process  for  more  than  twenty  years, 
during  the  whole  of  which  time,  although  many  other  methods  of 
producing  oxygen  were  proposed  and  tried  in  this  country  and 
abroad,  the  barium  process  remained  in  sole  possession  of  the  field. 
Furthermore,  it  is  worthy  of  note,  in  these  days  when  it  is  customary 
to  credit  any  country  but  our  own  with  industrial  enterprise,  that 
in  Germany,  France,  and  the  United  States,  the  oxygen  industry 
was  started  with  the  barium,  designed  and  erected  by  the  British 
Oxygen  Company,  who  have  acquired  the  British  patents  of  Pro- 
fessor Linde  and  Dr.  Hampson.  These  two  inventors  are  the  authors 
of  the  self -in  tensive  system  of  liquefying  air,  on  which  are  based  the 
numerous  processes  introduced  in  recent  years,  with  extravagant 
and  preposterous  claims  that  have  gone  far  to  bring  liquid  air 
into  disrepute.  A  serious  scientist  saw  long  ago  the  only  really 
valuable  commercial  application  of  oxygen  and  nitrogen.  For 
many  years  he  devoted  himself  to  adopting  his  system  of  liquefying 
air  for  this  purpose.  That  his  labours  have  been  crowned  with 
success  has  been  proved  by  the  fact  that  on  the  Continent  the  com- 
pany which  controls  his  patents  has  already  erected  a  large  number 
of  plants,  which  are  in  daily  operation,  giving  most  satisfactory 


MANUFACTURE  OF  OXYGEN  15 

results.  It  is  the  Linde  plant  that  the  British  Oxygen  Company 
erected  at  Westminster  and  many  other  great  centres. 

Briefly  expressed,  the  process  consists  of  liquefying  the  air  com- 
pletely in  the  first  instance  by  the  self -in  tensive  system.  Whilst 
obtaining  almost  complete  transference  of  heat  from  the  compressed 
air  entering  the  apparatus  to  the  liquefied  air,  the  liquid  is  submitted 
to  a  special  process  of  rectification,  by  means  of  which  oxygen  of 
any  degree  of  purity  up  to  98  or  99  per  cent,  can  be  obtained.  The 
plant  is  driven  by  a  Diesel  engine,  which  develops  som  35  h.p. 
Air  is  compressed  by  three  stage  compressors,  belt-driven.  Between 
each  stage  of  compression  the  air  is  restored  to  normal  temperature 
by  passing  through  coils  contained  in  a  cooler,  through  which  water 
circulates.  The  system  of  purification  of  the  air  is  very  complete;, 
all  the  moisture  and  carbolic  acid  being  practically  eliminated, 
first  in  the  purifiers  containing  unslaked  lime  and  calcium  chloride, 
while  the  final  traces  of  moisture  are  subsequently  removed  by 
freezing  in  a  forecooler,  which  is  employed,  partly  for  this  purpose, 
partly  to  precool  the  air  before  it  enters  the  separators.  The  lower 
part  of  the  forecooler  is  reduced  in  temperature  by  a  small  CO2 
refrigerating  machine  of  the  usual  type  made  by  the  Linde  British 
Refrigerating  Company,  but  the  upper  part  is  cooled  by  the  waste 
nitrogen  from  the  separator. 

The  interchange  is  so  effective  that,  before  the  nitrogen  is 
returned  to  the  atmosphere,  it  has  taken  so  much  heat  from  the  in- 
coming compressed  air  that  it  leaves  the  forecooler  only  a  few  degrees 
below  normal  temperature.  The  compressed  air,  on  the  other  hand, 
leaves  the  bottom  of  the  forecooler  at  a  temperature  considerably 
below  freezing-point,  and  then  enters  the  top  of  the  separator,  passing 
downwards  to  a  series  of  coils,  which  are  so  constructed  as  to  be 
surrounded  by  both  the  outgoing  cold  gases.  The  bottom  of  the 
separator  contains  liquid  air,  or,  more  correctly  speaking,  liquid 
oxygen.  The  compressed  air,  on  its  way  to  the  expansion  point,  is 
conveyed  through  the  liquid,  by  which  means  it  is  largely  con- 
densed. It  then  passes  through  the  regulating  valve,  at  which 
point  it  expands,  and  is  ultimately  discharged  into  the  top  of  an 
inner  central  chamber  which  forms  the  rectifying  column,  in  which 
the  separation  of  oxygen  and  nitrogen  is  effected,  oxygen  descend- 
ing in  a  liquid  state  to  the  bottom  of  the  separator,  nitrogen  ascend- 
ing in  a  gaseous  or  vaporous  condition  to  the  top. 

The  nitrogen  is  allowed  freely  to  discharge  into  the  atmo- 
sphere through  the  forecooler,  as  already  explained;  the  oxygen  is 
allowed  to  boil  off  in  any  desired  quantity  by  the  adjustment  of  a 


16  MODERN  METHODS  OF  WELDING 

discharge  valve.  Both  gases,  however,  on  leaving  the  separator, 
are  kept  in  intimate  contact  with  the  cells  conveying  the  incoming 
air,  so  that  before  leaving  the  apparatus  the  heat  of  the  incoming 
air  has  been  mostly  transferred  to  the  gases.  The  plant  is  very 
conveniently  arranged,  and  consists  of  two  separators  and  two  fore- 
coolers,  one  of  each  being  worked  at  a  time.  In  this  way  continuous 
working  is  ensured,  for  when  ice  (due  to  entrapped  traces  of  moisture 
in  the  air)  has  accumulated  to  such  an  extent  as  to  cause  a  stoppage 
in  one  separator,  the  other  can  be  put  in  operation,  whilst  the  first 
is  allowed  to  thaw.  In  practice,  freezing  is  found  to  occur  after  six 
to  seven  days  of  continuous  work. 

The  description  here  given  represents  the  normal  working  of  the 
plants.  But  before  pure  oxygen  can  be  produced  the  separator 
has  to  be  cooled  down,  and  a  considerable  quantity  of  liquid  pro 
duced.  This  operation  takes  about  three  hours,  during  which  time 
the  compressed  air  circulating  through  the  coils  is  (by  the  adjustment 
of  the  regulating  valve)  maintained  at  a  pressure  of  about  2,500 
pounds  per  square  inch.  Afterwards,  when  the  oxygen  is  being 
produced,  the  pressure  is  about  800  pounds  per  square  inch,  at  which 
pressure  it  continues  to  work. 

Oxygen  obtained  from  liquid  air  may  contain  more  or  less  nitro- 
gen. That  obtained  by  the  electrolysis  of  water  might  contain  a 
little  hydrogen.  These  two  gases  are  considered  as  impurities. 
If  hydrogen  were  present  to  an  appreciable  extent,  it  would  have  the 
disadvantage  of  forming  with  the  oxygen  an  explosive  mixture. 
It  has  been  demonstrated  that  in  the  cutting  of  iron  and  steel  by  the 
blowpipe  cutters,  the  presence  of  nitrogen,  even  in  small  quantities, 
has  an  adverse  effect  on  the  quality  and  rapidity.  Oxygen  com- 
pressed in  cylinders  is  generally  delivered  containing  96  to  99  per 
cent,  of  oxygen;  but  the  commercial  guarantee  may  be  as  low  as 
95  per  cent.  The  British  Oxygen  Company  guarantee  the  quality 
of  their  oxygen  as  98-5  to  99  per  cent.,  and  many  experiments  carried 
out  by  the  author  confirm  this. 

Analysis  is  conducted  by  acting  on  a  definite  volume  of  gas 
with  a  chemical  which  rapidly  absorbs  the  oxygen  and  leaves  the 
impurities  intact  (hydrogen,  nitrogen,  or  carbon  dioxide).  The 
quantity  of  gas  absorbed,  compared  with  the  original  volume,  gives 
the  degrees  of  purity.  The  analysis  is  generally  done  in  graduated 
test-tubes,  as  a  rule  of  100  centimetres  capacity  and  graduated 
0  to  100.  The  absorbent  liquid  takes  the  place  of  the  oxygen  ab- 
sorbed, so  that  when  the  reaction  is  over  it  is  only  necessary  to  read 
off  the  level  of  the  liquid  to  know  the  purity  of  the  oxygen. 


CHAPTER  IV 
MANUFACTURE  OF  HYDROGEN 

THESE  two  gases — oxygen  and  hydrogen — are  now  manufactured 
on  very  large  scales.  Hydrogen  can  be  very  much  more  freely 
obtained  than  in  the  past,  and  will  be  more  used  in  future  for  weld- 
ing purposes.  There  are  very  few  who  are  acquainted  with  oxy- 
hydrogen  as  applied  to  welding  at  the  present  time,  although  it  was 
in  extensive  use  until  the  advent  of  calcium  carbide  in  large  com- 
mercial quantities,  which  generate  the  acetylene  gas.  The  latter 
was  employed,  in  combination  with  oxygen,  for  use  in  the  blow- 
pipe for  welding,  giving  a  very  much  higher  temperature  of  6,000°  F. 
against  the  oxy-hydrogen  name's  4,000°  F. 

There  are  many  advantages  in  using  oxy-hydrogen  blowpipes. 
Firstly,  the  hydrogen  is  supplied  in  cylinders,  the  same  as  oxygen. 
Therefore  it  can  practically  be  used  anywhere.  There  is  no  wasted 
gas,  no  expense  in  initial  outlay  for  generators  or  fixing  of  piping, 
no  messy  substance  to  clear  away,  as  in  acetylene  generators,  the 
two  gases,  oxygen  and  hydrogen,  under  equal  pressures,  thus  ensur- 
ing a  constant,  steady  flame.  This  blowpipe  is  also  well  adapted  for 
the  burning  of  lead  and  the  welding  of  aluminium,  because  the  heat 
of  temperature  is  not  so  high,  but  is  suitable  for  these  metals.  How- 
ever, there  is  the  disadvantage  of  not  being  able  to  get  high  enough 
temperature  to  weld  heavy  mild  steel  or  cast  iron,  as  the  heat  is 
absorbed  and  there  is  loss  by  conductivity.  It  is  practically  im- 
possible to  weld  steel  plates  exceeding  TV  inch  thick. 

The  flame  is  produced  by  the  mixing  of  two  volumes  of  hydrogen 
and  one  of  oxygen.  This  is  the  theoretical  mixture;  but  the  author 
found  in  practice  that  it  required,  to  maintain  a  good  heat  to  com- 
plete a  proper  weld,  three  parts  of  hydrogen  to  one  of  oxygen. 
Hydrogen  and  oxygen  have  strong  affinity  for  each  other.  Their 
combination  occurs  with  great  explosive  violence,  the  product  being 
water  in  the  form  of  steam.  This  steam  is,  of  course,  superheated 
in  the  hot  flame,  which  process  of  dissociation  involves  a  consumption 
of  heat,  which  is  abstracted  from  the  flame,  hence  an  oxidising  effect 
on  the  weld.  This  can  only  be  avoided  by  feeding  the  flame. with 


18  MODERN  METHODS  OF  WELDING 

an  excess  of  hydrogen  (in  practice  four  to  five  volumes  of  hydrogen 
to  one  of  oxygen),  whilst,  on  the  other  hand,  only  that  amount  of 
heat  can  be  obtained  which  is  disengaged  in  the  combination  of  the 
two  volumes  of  hydrogen  and  one  of  oxygen.  The  large  excess  of 
hydrogen  required  to  prevent  oxidation  furnishes  in  itself  one  way 
why  welding  by  means  of  the  hydrogen-oxygen  flame  is  frequently 
uneconomical.  A  further  reason,  however,  lies  in  the  fact  that  the 
temperature  of  the  flame,  in  consequence  of  this  excess  of  hydrogen, 
is  essentially  lower  than  it  ought  to  be.  In  spite  of  this,  it  is  found 
in  practice  that  for  thin  plate  welding  the  oxy-hydrogen  blowpipe 
has  certain  advantages.  The  flame  is  more  diffused  than  in  the  case 
of  oxy-acetylene  flame,  hence  less  liable  to  melt  through  and  pierce 
the  metal. 

Every  student,  if  he  is  to  become  a  welder,  must  have  a  fair 
knowledge  of  all  the  materials  used  and  their  constituents,  as  also 
of  the  gases  such  as  oxygen,  hydrogen,  and  acetylene.  Since  these 
gases  are  usually  provided  in  convenient  cylinders  for  commercial 
purposes,  the  users  as  a  rule  are  not  acquainted  with  their  manu- 
facture or  with  the  source  of  supply.  But  it  is  really  essential  that 
the  users  of  these  gases  should  be  acquainted  with  the  process  of 
manufacturing  them.  It  is  probable  that  the  war,  which  has  brought 
home  to  many  engineers  and  business  men  how  easily  hydrogen  and 
oxygen  can  be  generated,  will  lead  to  an  increased  demand  for  these 
gases  and  to  their  wider  appreciation  in  industrial  processes. 

Where  both  the  decomposition  products  of  water,  hydrogen, 
and  oxygen  can  be  utilised,  electrolytic  generation  offers  advantages 
over  the  isolation  of  hydrogen  from  water-gas,  which  is  a  cheaper 
method  when  worked  on  a  really  large  scale.  In  the  laboratory 
the  electrolysis  of  water  is  a  very  simple  matter.  The  electrodes 
are  placed  in  acidulated  water  in  a  glass  cell.  Each  electrode  is 
surrounded  by  a  hood  (an  inverted  test-tube,  e.g.,  in  which  the  gas 
evolved  collects).  Currents  of  about  two  volts  give  one  volume  of 
oxygen  and  two  of  hydrogen. 

The  technical  electrolyser  is  not  quite  so  simple  as  the  laboratory 
cell.  The  design  and  construction  of  automatic  apparatus  which 
will  continuously  yield  both  gases  in  a  pure  condition  of  90  per  cent, 
and  more,  practically  without  requiring  any  attendance,  have  left 
suincient  scope  for  the  ingenuity  of  inventors.  Glass  cells  being 
out  of  the  question,  the  container  has  to  be  adapted  to  the  electro- 
lyte. Water  itself  is  a  poor  conductor  to  serve  as  an  electrolyte. 
Either  sulphur  acid  or  caustic,  both  of  about  20  per  cent,  concen- 
tration, are  used ;  but  the  chemicals  are  merely  to  increase  the  con- 


MANUFACTURE  OF  HYDROGEN  19 

ductivity  of  the  water,  which  is  the  electrolyte,  and  has  to  be  re- 
plenished by  feeding  distilled  water  into  the  cells.  The  impurities 
of  ordinary  water,  notably  chlorine,  would  tend  to  corrode  the 
apparatus. 

The  acid  is  placed  in  lead  containers,  the  alkali  in  iron  cells. 
The  reversible  decomposition  of  the  water  itself  would  only  require 
1-23  volts;  but  the  potential  applied  has  to  overcome  the  resistance 
of  the  leads  and  of  the  electrolyte,  and  further  the  polarisation  of 
the  electrodes  by  the  gases  liberated.  Sulphuric  acid  is  a  better 
conductor  than  alkali,  but  the  supertension  of  the  lead  cathode  is 
decidedly  higher.  Hence,  on  the  whole,  the  caustic  alkali  requires 
a  lower  decomposition  potential.  As  regards  gas  purity  and,  to  a 
certain  extent,  the  efficiency,  there  is  not  much  to  choose  between 
the  acid  and  the  alkali  processes,  though  the  number  of  kilowatt 
hours  required  for  the  liberation  of  35  cubic  feet  of  the  two  gases 
varies  from  6  down  to  about  3-5,  at  volts  ranging  from  3-6  down 
to  2-3.  But  in  all  these  figures  the  decimals  become  important, 
and  there  are  features  justifying  a  careful  selection  of  a  type  of 
electrolyser. 

The  general  preference  is  for  alkali  cells.  In  the  Schoop  acid 
eleotrolysers,  the  two  groups  of  electrodes,  anodes,  and  twice  as 
many  cathodes,  are  all  lead  tubes,  open  below  to  let  the  acid  act 
on  the  lead  wires  in  the  tube.  Each  tube  is  insulated  by  a  refractory 
hood.  The  groups  are  coupled  in  parallel. 

In  the  Garute  alkali  electrolyser,  vertical  diaphragms  of  iron 
separate  the  iron  tank  into  anode  and  cathode  compartments, 
the  two  groups  of  iron  electrodes  being  again  in  parallel. 

The  Schukert  electrolyser  uses  insulating  diaphragms  and  places 
iron  hoods  in  the  different  compartments  to  collect  the  gases. 

The  Schmidt  cell  of  the  Oerlikon  Company  is  of  the  filter -press 
type,  and  the  corrugated  iron  electrodes  are  coupled  in  series.  They 
are,  in  fact,  bipolar,  as  in  some  electrolytic  copper  baths  and  in 
bleach  cells. 

The  electrolysers  of  the  Integral  Oxygen  Company,  London, 
illustrated  on  p.  20,  differ  from  types  mentioned  above  in  so  far 
as  each  cell  is  self-contained,  in  having  two  electrode  units,  and, 
further,  as  to  arrangements  made  for  the  regulation  of  the  gas 
pressure.  This  is  an  Integral  unit  generator.  The  cells  are  of  the 
Hayard-Flamand  type.  The  early  patents  of  this  cell  date  back  to 
1900,  but  the  particulars,  the  feed  and  pressure  regulation,  are  later 
inventions.  The  battery  photograph  seems  to  suggest  a  filter-press 
arrangement,  but  each  cell  is  independent,  and  the  common  features 


20 


MODERN  METHODS  OF  WELDING 


are  the  water  and  the  gas  pipes  and  the  grouping  in  series.  Each 
cell  is  independent,  each  has  its  own  feed  and  discharge  devices, 
each  consists  of  a  thin,  rectangular  frame  of  cast  iron,  to  which  two 
cast-iron  plates,  the  electrodes,  are  bolted,  mica  insulators  being 
interposed. 

The  asbestos  diaphragm  divides  the  space  of  the  flat  cell  vertically 
into  two  halves,  an  anode  compartment  and  a  cathode  compartment. 
Each  compartment  communicates  through  two  ports  with  a  gas 
chamber.  The  right  is  the  water  chamber.  Several  jars  and  pipes 


FIG.  8. — 4,000 -UNIT  GENERATORS  FOR  PRODUCING  OXYGEN  AND  HYDROGEN. 

will  be  seen  on  the  top  of  the  gas  chamber.  The  gas  leaves  through 
the  two  outer  glass  jars — the  hydrogen  through  the  jar  on  the  right, 
the  oxygen  through  that  on  the  left — and  enters  the  two  gas  pipes 
which  are  in,  but  not  on,  the  sketch.  A  third  pipe  is  the  distilled- 
water  pipe.  This  is  connected  with  the  central  jar  through  which 
the  cell  is  originally  charged  with  caustic  soda  of  20  per  cent.  The  cell 
discharges  a  spray  of  gas  and  caustic  soda ;  this  frothy  liquid  spreads 
upon  the  base  plate,  which  has  a  raised  edge,  this  ridge  preventing 
the  liquid  from  running  back  into  the  port  and  choking  it.  It 
spreads  over  to  the  port  and  there  flows  back  into  the  cell.  Thus 
a  kind  of  circulation  is  set  up ;  the  gas  itself  is  further  deprived  of  its 


MANUFACTURE  OF  HYDROGEN  21 

moisture  by  having  to  force  its  way  through  a  gas  tap  in  the  glass  jar, 
which  contains  an  inverted  bell  of  iron.  The  liquid  is  intercepted 
between  this  bell  and  the  jar,  the  top  of  which  is  joined  to  the  gas 
pipe.  The  cells  are  worked  at  a  temperature  of  about  55°  C.  The 
guaranteed  purity  of  the  gases  evolved  is  oxygen  99  per  cent., 
hydrogen  99-5  per  cent.  During  recent  trials  at  Farnborough  the 
oxygen  purity  was  maintained  at  99-8  per  cent.,  which  was  an 
exceptionally  high  figure. 

It  must  be  noted  that  the  gases  are  not  purified  in  any  way,  but 
enter  the  gas  holders  or  cylinders  as  they  leave  the  glass  jars.  The 
average  potential  is  about  2-2  or  2-3  volts  per  cell,  at  the  normal 
current  of  about  600  amperes.  Each  cell  has  a  rated  output  of 
4-8  cubic  feet  of  oxygen  and  9-6  of  hydrogen,  and  gives  an  average 
yield  of  4  cubic  feet  of  oxygen,  and  twice  as  much  hydrogen. 


CHAPTER  V 
MANUFACTURE  OF  CARBIDE 

THE  manufacture  of  calcium  carbide  is  carried  out  on  such  exten- 
sive lines  that  any  student  of  welding  should  make  himself  conver- 
sant with  its  manufacture.  Acetylene  was  discovered  by  Davy 
in  the  chemical  laboratory  in  the  year  1836.  Many  methods  of 
preparing  the  gas  were  described  by  various  experimenters,  the 
majority  of  which  are  only  of  academic  interest.  But  it  may  be 
mentioned  that  in  1840  Hare,  by  heating  in  an  electric  arc  a  black 
residue  obtained  by  heating  a  mixture  of  mercuric  cyanide  and 
lime,  arrived  at  a  compound  which  was  undoubtedly  calcium  car- 
bide, although  not  recognised  as  such  at  the  time. 

The  next  date  of  importance  is  the  year  1862,  in  which  the  German 
chemist  Woehler  (whose  name  is  well  known  amongst  chemists  as 
the  discoverer  of  synthetic  urea  and  other  important  bodies,  includ- 
ing aluminium)  obtained  "  calcium  of  carbide  "  decomposed  water 
with  formation  of  calcium  hydrate  and  acetylene.  It  is  hard, 
really,  to  say  who  was  the  actual  discoverer  of  calcium  carbide. 
It  was  Moisson,  "  the  king  of  experimental  savants,"  who  published 
his  classic  investigations.  His  results  were  obtained  as  factors  in  a 
magnificent  research,  every  step  in  which  was  logically  worked  out 
and  verified;  a  research  which  will  ever  stand  out  as  a  scientific 
classic .  But  the  fact  remains  that  he  only  attained  and  published  the 
discovery  of  the  direct  formation  of  calcium  carbide  in  the  electric 
furnace  to  find  that  his  work  had  been  forestalled  by  a  few  months 
by  the  chance  observation  of  an  engineer  who,  although  devoid  of 
chemical  knowledge,  yet  had  sufficient  acumen  to  grasp  the  commer- 
cial importance  of  the  discovery.  Anyone  who,  with  a  mind  free 
from  prejudice,  reads  the  evidence  on  this  subject,  is  forced  to  the 
conclusion  that  the  world  owes  "  commercial  acetylene  "  to  the 
Canadian  engineer,  Willson,  and  the  shrewd  business  men  who 
supported  him. 

Moisson  obtained  crystallised  calcium  carbide  during  a  systema- 
tic and  masterly  research  upon  the  products  of  the  electric  furnace. 
His  first  paper  described  an  electric  furnace,  which  he  distinctly 
stated  was  not  an  industrial  apparatus,  but  for  research  purposes 

22 


MANUFACTURE  OF  CARBIDE  23 

only.  His  work  consisted  in  the  preparation  of  crystallised  metallic 
oxides  such  as  those  of  calcium,  strontium,  barium,  magnesium, 
aluminium,  iron,  chromium,  etc.  He  then  dealt  with  fusion  and 
volatilisation  of  some  refractory  bodies  and  metals.  This  was 
followed  by  his  classical  research  on  the  different  varieties  of  carbon 
and  the  formation  of  the  diamond.  The  description  of  the  forma- 
tion of  calcium  carbide  is  included  in  a  study  of  the  carbides, 
silicides,  and  the  borides.  After  a  brief  review  dealing  with  the 
work  of  Berthelot,  Woehler,  and  Travers,  who  in  1893  obtained  a 
mixture  containing  some  carbide,  Moisson  writes : 

;'  The  question  had  reached  this  point  when,  in  a  note  appearing 
in  the  Comptes  Rendus  de  V Academic  des  Sciences  on  December  12, 
1892,  I  made  public  for  the  first  time  the  formation  in  the  electric 
furnace  of  a  carbide  of  calcium  fusible  at  a  high  temperature. 
This  is  what  I  wrote  on  the  subject.  If  the  temperature  reaches 
3,000°  C.,  even  the  furnace  material,  the  quicklime,  melts  and  flows 
like  water.  At  this  temperature  the  carbon  quickly  reduces  the 
oxide  of  calcium  (lime),  the  metal  itself  is  liberated  in  abundance; 
it  unites  readily  with  the  carbon  of  the  electrodes  to  form  a  carbide 
of  calcium,  liquid  at  a  red  heat,  which  is  easy  to  recover.  Follow- 
ing this  research,  I  presented  to  the  Academie  des  Sciences  a  note 
of  carbide  of  calcium  on  March  5,  1894,  another  note  of  carbides 
of  barium  and  strontium  on  March  9,  1894.  In  this  work  I  showed 
that  in  a  high  temperature  of  the  electric  furnace  there  exists  only 
one  compound  of  carbon  and  calcium.  This  compound  was  crystal- 
line; I  established  its  formula  by  analysis,  and  in  the  study  of  its 
properties  I  made  it  clear  that  the  bodies  decompose  in  water, 
liberating  the  gas  acetylene  absolutely  pure." 

This  was  the  starting-point  of  the  acetylene  industry. 

At  the  end  of  a  patent,  No.  492,377,  U.S.A.,  on  the  preparation 
of  aluminium  bronze,  M.  Thos.  Willson  made  an  allusion  to  an  inter- 
minate  carbide  of  calcium  as  well  as  to  a  great  number  of  other 
bodies,  elements  or  compounds,  but  did  not  give  an  analysis  of  the 
two  compounds  obtained,  nor  even  mentioned  that  this  product 
decomposes  cold  water  with  liberation  of  any  gas  whatever.  He 
also  avoided,  with  the  greatest  care,  that  "  bath  of  fusion  "  brought 
metallic  calcium. 

Moisson  prepared  his  carbide  by  making  an  intimate  mixture  of 
120  grammes  of  lime  from  marble,  and  70  grammes  of  carbonised 
sugar,  heating  for  fifteen  minutes  in  a  crucible  in  the  electric  furnace 
with  a  current  of  350  amperes  and  70  volts.  He  used  a  slight  excess 
of  lime  to  counteract  the  carbon  obtained  from  the  crucible.  He 


24  MODERN  METHODS  OF  WELDING 

noted  that  if  any  impure  lime  was  used,  containing  sulphates,  phos- 
phates, or  silica,  these  impurities  would  be  found  in  the  acetylene 
liberated  from  the  carbide.  Moisson  carried  out  a  number  of  experi- 
ments with  impure  materials  and  analysed  the  gas  obtained;  also 
studied  the  physical  qualities  of  the  carbide,  the  gas  yield  as  well 
as  its  chemical  properties  and  that  of  acetylene.  It  is  interesting 
to  note  that  he  states  that  "  pure  and  dry  "  nitrogen  does  not  react 
with  carbide  even  at  1,200°  C.  Had  he  continued  this  experiment 
to  a  higher  temperature  he  would  have  probably  been  the  discoverer 
of  cyanamide. 

Whatever  the  facts  of  the  case  may  be,  Moisson's  systematic 
and  scientific  research  work  and  the  practical  results  obtained 
place  his  name  for  ever  in  an  unassailable  position  in  the  history  of 
the  industry.  From  the  time  when  Moisson  and  Willson  published 
their  investigations,  the  accepted  equation  for  the  production  of 
calcium  of  carbide  in  the  electric  furnace  from  carbonaceous  matter 
and  lime  has  always  been — 

CaO+3C-CaC2+CO. 

This  final  result  may  be  approximately  the  production  of  two 
compounds,  CaC2  and  CO;  but  the  reaction,  or  rather,  reactions 
which  take  place  before  the  final  stage  is  reached  certainly  appear 
to  be  far  more  complex.  The  conversion  of  the  raw  material  into 
carbide  appears  to  take  place  in  steps. 

In  the  past,  every  person  who  had  cheap  water-power  available 
believed  that  he  had  the  Alpha  and  Omega  for  making  cheap  carbide, 
even  if  there  was  no  limestone  or  carbon  within  hundreds  of  miles. 
To  equip  a  modern  factory,  a  very  large  capital  is  required,  and  a 
suitable  site,  where  cheap  water-power  is  available,  near  to  lime- 
stone, coal,  and  coke.  The  power  for  electric  energy,  in  the  case  of 
every  carbide  factory  in  existence,  is  supplied  from  a  hydro-electric 
station,  where  the  prime  mover,  or  force,  is  falling  water — in  other 
words,  a  waterfall.  This  falling  water  passes  through  turbines  or 
Pel  ton  wheels.  The  type  of  turbine  is  decided  by  the  head  or  volume 
of  water  available.  These  turbines  drive  dynamos  or  electric 
generators ;  some  of  these  generators  are  used  in  the  electric  furnaces 
for  the  melting  of  the  carbon  and  the  lime  for  producing  the  carbide 
of  calcium. 

An  electric  carbide  furnace  as  a  rule  consists  simply  of  a  steel  case 
or  box,  or  a  steel-framed  case  or  box  lined  inside  with  suitable 
refractory  material,  having  a  tapping  hole  very  similar  to  a  tapping 
hole  in  an  iron-furnace  or  cupola.  In  some  of  the  furnaces  electrodes 
are  fixed  in  the  bottom  of  the  furnace;  in  others  the  electrodes  are 


MANUFACTURE  OF  CARBIDE  25 

suspended  from  the  top.  Each  of  the  electrodes  is  held  in  various 
kinds  of  holders,  which  are  connected  to  busbars.  The  electrodes 
are  made  of  carbon.  The  materials  used  in  the  manufacture  of 
carbide  of  calcium  are  primarily— 

(a)  Carbon  for  the  charge  in  the  form  of  coal  or  coke, 
(6)  Carbon  for  the  electrodes, 
(c)  Lime. 

Coal.  —  Only  one  form  of  coal,  anthracite,  has  up  to  the  present 
given  anything  like  satisfactory  results.  An  anthracite  coal  con- 
taining not  more  than  4  per  cent,  of  ash  and  not  more  than  0-040 
per  cent,  of  phosphorus  will  serve  admirably  in  a  modern  furnace. 

Limestone.  —  Mountain  limestone  is  the  stone  composing  the 
limestone  ranges  known  to  most  of  us.  The  best  stone  is  found  in 
the  Buxton  and  Settle  Hills  districts.  There  is  also  oolitic  limestone 
(so  called  because  of  the  resemblance  to  a  mass  of  fish  roe),  made  up 
of  small  rounded  grains  of  carbonate  of  lime.  Chalk  is  fine-grained 
limestone,  consisting  of  finely  commuted  shells.  Magnesia  lime- 
stone is  a  limestone  mixed  with  more  or  less  magnesia.  This  is 
very  suitable  for  carbide-making.  The  principal  impurities  present 
in  limestone  used  for  carbide-making  are  magnesia,  alumina,  silica, 
iron  oxide,  sulphur,  and  alkalies.  The  maximum  quantities  of 
impurities  permissible  in  good  limestone  for  carbide  should  be 
about  0-50  per  cent,  of  magnesia  (MgO),  0-50  per  cent,  of  alumina 
and  iron  oxide,  0-01  per  cent,  of  phosphoric  acid  (P2Os)>  about  1  to 
1-2  per  cent,  of  silica  (Si02),  and  only  traces  of  sulphur.  This 
corresponds  to  a  stone  containing  about  97  to  98  per  cent,  of 
carbonate  of  lime. 

Carbide,  as  now  made  by  a  first-class  factory,  yields  310  litres 
per  kilogramme  (4-95  feet  per  pound),  and  contains,  therefore, 
89  per  cent,  of  pure  carbide,  11  per  cent,  of  impurities.  A  metric 
ton  of  commercial  carbide  will  contain  890  kilogrammes  of  pure 
carbide.  To  produce  this  890  kilogrammes  of  pure  carbide  in  a 
metric  ton,  based  on  the  lime  of  96  per  cent,  purity,  coke  with  6  per 
cent,  of  ash,  the  following  will  be  theoretically  the  quantities  of  raw 
materials  for  a  metric  ton  of  carbide  — 

Lime  ^  =  811  kilogrammes. 

64     0-96 


Total  kilogrammes  1,332  =  2,797  pounds. 
(1  kilogramme  =2-2  pounds.) 


26  MODERN  METHODS  OF  WELDING 

Therefore  it  takes  1,332  kilogrammes  of  materials  to  produce 
890  kilogrammes  of  commercial  caibide.  Carbide  is  produced  in 
the  electric  furnace  by  the  fusion  of  coal  approximately  36  parts 
by  weight,  lime  56  parts  by  weight,  to  a  temperature  reaching 
4,000°  C. 

Under  the  enormous  temperature  of  the  electric  furnace  (which 
is  carried  by  the  carbon  electrodes)  the  lime  and  carbon  combine. 
The  liquid  carbide  which  results  is  tapped  from  the  furnace  (the  same 
as  the  blast  furnace  or  foundry  cupola)  into  receptacles  which, 
when  cooled,  are  transported  to  the  crushing  machines,  which  break 
them  up.  Then  on  the  mechanical  graders,  which  separate  the 
various  sizes;  the  carbide  is  then  packed  into  drums,  and  the 
covers  are  hermetically  sealed. 

The  formula  of  carbide  of  calcium  is  represented  by  CaC2 ;  it 
is  made  of  62-5  per  cent,  of  calcium. 

Use  14  pints  of  water  to  each  pound  of  carbide  in  water-to- 
carbide  generators,  5  pints  of  water  in  carbide-to-water  generators. 
This  should  assure  full  decomposition.  Carbide  should  yield 
4-8  cubic  feet  of  acetylene  for  every  pound  of  carbide  placed  in 
the  generating  chambers.  There  are  various  apparatus  for  testing 
the  carbide  on  the  market.  When  a  sample  is  tested  it  must  be 
broken  up  in  a  mortar  to  about  J-inch  mesh,  then  screened  to 
remove  the  dust  as  rapidly  as  possible,  then  weighed  out  in  a  limited 
quantity  accurately  by  a  chemist's  scale.  The  carbide  is  then 
placed  in  the  generating  chambers  immediately,  the  water  turned 
on  (the  height  of  the  bell  should  be  marked  before  the  water 
is  turned  on);  then,  when  the  generation  has  ceased,  the  bell 
should  be  marked  and  then  measured  with  the  already  provided 
instruments. 


CHAPTER  VI 
ACETYLENE 

ACETYLENE  or,  as  it  is  scientifically  named,  "ethine,"  is  a  simple 
hydrocarbon  consisting  of  24  parts  by  weight  of  carbon  and 
2  parts  by  weight  of  hydrogen;  its  chemical  symbol,  C2H2, 
meaning  it  is  a  compound  of  two  atoms  of  carbon  combined  with  two 
atoms  of  hydrogen.  It  is  a  clear,  colourless  gas,  of  a  specific  gravity 
of  0-92.  It  is,  owing  to  its  synthetic  formation,  the  most  pure, 
at  the  same  time  nearly  the  richest  hydrocarbon  gas,  containing 
no  less  than  92-5  per  cent,  of  carbon  when  perfectly  pure  and  free 
from  water  vapour.  It  has  an  illuminating  value  of  50  candle- 
power  per  cubic  foot. 

It  has  a  most  unmistakable  and  penetrating  odour.  When 
present  in  the  proportion  of  only  1  part  in  10,000  parts  of  air  it 
is  distinctly  perceptible  long  before  there  is  sufficient  gas  present 
to  cause  explosion.  Therefore  it  can  be  at  once  detected,  and  an 
explosion  prevented.  One  burner  passing  1  cubic  foot  per  hour 
in  a  room  of  2,500  cubic  feet  area  for  a  period  of  nine  or  ten  hours 
would  not  be  sufficient,  with  the  same  quantity  of  air,  to  make  an 
explosive  mixture.  The  largest  acetylene  burners  only  pass  1  cubic 
foot  per  hour,  against  the  5  cubic  feet  of  coal-gas.  It  is,  therefore, 
obvious  that  the  prevailing  popular  belief  as  to  acetylene  being 
more  dangerous  than  coal-gas  is  a  fallacy. 

Acetylene  and  oxygen  ignite  at  a  temperature  of  400°  C.  The 
temperature  of  combustion  is  4,000°  C.  Acetylene,  although 
practically  pure  gas,  ^usually  contains  some  impurities  in  a  greater 
or  less  proportion,  mostly  sulphuretted  and  phosphuretted  hydrogen 
due  to  the  presence  of  sulphate  of  calcium,  gypsum,  and  calcium 
phosphide  in  the  lime,  or  to  the  sulphur  and  phosphorus  in  the 
coal  and  coke.  Acetylene  is  always  contaminated  with  ammonia, 
formed  by  the  combination  of  nitrogen  derived  from  the  coke  with 
the  hydrogen  of  the  water  during  decomposition  of  the  carbide. 
That  acetylene  is  a  poisonous  gas  has  been  proved  to  be  untrue. 
When  pure  it  is  relatively  harmless.  The  range  of  explosibility 
is  wider  in  the  case  of  acetylene  than  of  coal-gas.  Mixtures  having 
less  than  5  and  more  than  60  per  cent,  are  practically  non-explosive. 

27 


28  MODERN  METHODS  OF  WELDING 

Acetylene,  being  an  endothermic  compound,  is  liable,  when  pure, 
if  compressed  without  at  the  same  time  being  cooled,  to  explode 
spontaneously.  Acetylene  is  soluble  in  water  and  many  other 
liquids.  It  can  be  liquefied  at  a  pressure  of  about  325  pounds  per 
square  inch  and  forms  a  mobile  and  highly  refractory  liquid,  much 
lighter  than  water. 

The  reactions  that  occur  when  carbide  and  water  are  brought 
into  contact  belong  to  the  class  which  chemists  usually  term  double 
decompositions.  Calcium  carbide  is  a  chemical  compound  of  a  metal 
calcium  with  carbon  containing  one  chemical  "part,"  or  atomic 
weight,  of  the  former  united  to  two  chemical  parts  of  the  latter. 
Its  composition  is  expressed  in  symbols  by  CaC2.  Similarly,  water 
is  a  compound  of  two  chemical  parts  of  hydrogen  with  one  of  oxygen, 
its  formula  being  H2O.  When  these  two  substances  are  mixed  to- 
gether, the  carbon  of  the  calcium  carbide  leaves  the  calcium  unit- 
ing together  to  form  that  particular  compound  of  hydrogen  and 
carbon,  or  hydrocarbon,  which  is  known  as  acetylene,  whose  formula 
is  C2H2,  while  the  residual  calcium  and  oxygen  join  together  to 
produce  calcium  oxide  of  lime  (CaO).  Put  into  the  usual  form  of  an 
equation,  the  reaction  proceeds  thus : 

CaC2  +  H20  =  C2H2  +  CaO.  (1) 

This  equation  not  only  means  that  calcium  carbide  and  water 
combine  to  yield  acetylene  and  lime ;  it  also  means  that  one  chemical 
part  of  car^rle  reacts  with  one  chemical  part  of  water  to  produce  one 
chemical  part  of  acetylene,  one  of  lime.  But  these  four  chemical 
parts,  or  molecules,  which  are  equal  chemically,  are  not  equal  in 
weight,  although,  according  to  the  common  law  of  chemistry,  they 
each  are  a  fixed  proportion  one  to  the  other.  Hitherto,  for  the  sake 
of  simplicity,  the  by-product  in  the  preparation  of  acetylene  has  been 
described  as  calcium  oxide,  or  quicklime.  It  is,  however,  one  of  the 
characteristics  of  this  body  to  be  hygroscopic,  or  greedy  of  moisture, 
so  that  if  it  is  brought  into  the  presence  of  water,  either  in  the  form 
of  liquid  or  vapour,  it  immediately  combines  therewith  to  yield 
calcium  hydroxide,  or  slaked  lime,  whose  chemical  formula  is 
Ca(OH)2.  Accordingly,  in  actual  practice,  when  calcium  is  mixed 
with  an  excess  of  water,  a  secondary  reaction  takes  place  over  and 
above  that  indicated  by  equation  (1),  the  quicklime  produced  com- 
bining with  one  chemical  part  or  molecule  of  water,  thus : 

CaO+H20=Ca(OH)2. 

As  these  two  actions  occur  simultaneously,  it  is  more  usual  and 
more  in  agreement  with  the  phenomena  of  an  acetylene  generator 


ACETYLENE  29 

to  represent  the  decomposition  of  calcium  carbide  by  the  combined 
equation : 

CaC2  +  2H20  =  C2H2  +  Ca(HO)2.  (2) 

By  the  aid  of  calculations  analogous  to  those  employed  in  the 
preceding  paragraph,  it  will  be  noticed  that  equation  (2)  states  that 
1  molecule  of  calcium  carbide,  or  64  parts  by  weight,  combines 
with  2  molecules  of  water,  or  36  parts  by  weight,  to  yield  1  molecule, 
or  26  parts  by  weight,  of  acetylene,  and  1  molecule,  or  74  parts  by 
weight,  of  calcium  hydroxide  (slaked  lime).  Here,  again,  if  more 
than  36  parts  of  water  are  taken  for  every  64  parts  of  calcium  carbide, 
the  excess  of  water  over  these  36  parts  is  left  undecomposed ;  and 
in  the  same  fashion,  if  less  than  36  parts  of  water  are  taken  for  every 
64  parts  of  calcium  carbide,  some  of  the  latter  must  remain  un- 
attacked,  whilst,  obviously,  the  amount  of  acetylene  liberated  cannot 
exceed  that  which  corresponds  with  the  quantity  of  substance  suffer- 
ing complete  decomposition.  If,  for  example,  the  quantity  of  water 
present  in  a  generator  is  more  than  chemically  sufficient  to  attack 
all  the  carbide  added,  however  large  or  small  that  excess  may  be, 
no  more,  and,  theoretically  speaking,  no  less,  acetylene  can  ever 
be  evolved  than  26  parts  by  weight  of  gas  for  every  64  parts  by 
weight  of  calcium  carbide  consumed.  It  is,  however,  not  correct  to 
invert  the  proposition,  and  to  say  that  if  the  carbide  is  in  excess  of 
water  added,  no  more,  and,  theoretically  speaking,  no  less,  acetylene 
can  be  involved  than  26  parts  by  weight  of  gas  for  every  36  parts 
of  water  consumed,  as  might  be  gathered  from  equation  (2) ;  because 
equation  (1)  shows  that  26  parts  of  acetylene  may,  on  occasion,  be 
produced  by  the  decomposition  of  18  parts  by  weight  of  water. 

From  the  purely  chemical  point  of  view  this  apparent  anomaly 
is  explained  by  the  circumstances  that  of  the  36  parts  of  water 
present  on  the  left-hand  side  of  equation  (2)  only  one-half — i.e., 
18  parts  by  weight — are  actually  decomposed  into  hydrogen  and 
oxygen,  the  other  18  parts  remaining  unattacked,  and  merely 
attaching  themselves  as  "water  of  hydration"  to  the  56  parts  of 
calcium  oxide  in  equation  (1)  so  as  to  produce  74  parts  calcium 
hydroxide  appearing  on  right-hand  side  of  equation  (2).  When 
the  output  of  gas  is  measured  in  terms  of  the  water  decomposed, 
in  no  commercial  apparatus,  and,  indeed,  in  no  generator  which  can 
be  imagined  fit  for  actual  employment  does  that  output  of  gas  ever 
approach  the  quantitative  amount,  but  the  volume  of  the  water  used, 
if  not  actually  disappearing,  is  always  vastly  in  excess  of  the 
requirements  of  equation  (2).  On  the  contrary,  when  the  make  of  gas 
is  measured  in  the  terms  of  the  calcium  carbide  consumed,  a 


30  MODERN  METHODS  OF  WELDING 

percentage  may  be  reached  of  80,  90,  or  even  99  per  cent,  of  what 
is  theoretically  possible.  Inasmuch  as  calcium  carbide  is  the  only 
costly  ingredient  in  the  manufacture  of  acetylene  so  long  as  it  is  not 
wasted — so  long,  that  is  to  say,  as  nearly  the  theoretical  yield  of 
gas  is  obtained  from  it — an  acetylene  generator  is  satisfactory  or 
efficient  in  this  particular ;  and,  except  for  the  matter  of  solubility, 
the  quantity  of  water  consumed  is  of  no  importance  whatever. 

The  chemical  action  between  calcium  carbide  and  water  is  accom- 
panied by  a  large  involution  of  heat,  which,  unless  due  precautions 
are  taken  to  prevent  it,  raises  the  temperature  of  the  substances 
employed,  and  of  the  apparatus  containing  them,  to  a  serious  and 
often  inconvenient  extent.  This  phenomenon  is  the  most  important 
of  all  in  connection  with  acetylene  manufacture,  for  upon  a  proper 
recognition  of  it,  and  upon  the  character  of  the  precautions  taken 
to  avoid  its  numerous  evil  effects,  depend  the  actual  value  and 
capacity  for  smooth  working  of  an  acetylene  generator.  Just  as, 
by  an  immutable  law  of  chemistry,  a  given  weight  of  calcium  carbide 
yields  a  given  weight  of  acetylene,  and  by  no  amount  of  ingenuity 
can  be  made  to  produce  either  more  or  less,  so,  by  an  immutable  law 
of  physics,  the  decomposition  of  a  given  weight  of  calcium  carbide 
by  water,  or  the  decomposition  of  a  given  weight  of  water  by  calcium 
carbide,  yields  a  definite  quantity  of  heat — a  quantity  of  heat  which 
cannot  be  reduced  or  increased  by  any  artifice  whatever. 

A  very  little  experiment  will  show  that  a  notable  quantity  of  heat 
is  set  free  when  calcium  carbide  is  brought  into  contact  with  water, 
and,  by  arranging  the  details  of  the  apparatus  in  a  suitable  manner, 
the  quantity  of  heat  manifested  may  be  measured  with  considerable 
accuracy.  A  lengthy  description  of  the  method  performing  this 
operation  is  unnecessary.  It  is  sufficient  to  say  that  the  heat  is 
estimated  by  decomposing  a  known  weight  of  carbide  by  means  of 
water  in  a  small  vessel  surrounded  on  all  sides  by  a  carefully  jacketed 
receptacle  full  of  water,  provided  with  a  sensitive  thermometer. 
The  quantity  of  the  water  contained  in  the  outer  vessel  being  known, 
and  its  temperature  having  been  noted  before  the  reaction  com- 
mences, an  observation  of  the  thermometer  after  the  decomposition 
is  finished,  when  the  mercury  has  reached  its  highest  point,  gives  data 
which  show  that  the  reaction  between  water  and  a  known  weight  of 
calcium  carbide  produces  sufficient  in  amount  to  raise  a  known  weight 
of  water  through  a  known  thermometric  distance;  and  from  these 
figures  the  corresponding  number  of  calories  may  easily  be  calculated. 

It  is  well  to  remark  that  there  is  scarcely  any  feature  in  the 
generation  of  acetylene  from  calcium  carbide  and  water — certainly 


ACETYLENE  31 

no  important  feature — which  introduces  into  practice  principles 
not  already  known  to  chemists  and  engineers.  Once  the  gas  is  set 
free,  it  ranks  simply  as  an  inflammable,  moisture-laden,  somewhat 
impure,  illuminating  and  heat-giving  gas,  which  has  to  be  dried, 
purified,  stored,  and  led  to  the  place  of  combustion.  It  is  in  this 
respect  precisely  analogous  to  coal-gas.  Even  the  actual  generation 
is  only  an  exothermic,  or  heat-producing,  reaction  between  a  solid 
and  a  liquid,  in  which  the  rise  in  temperature  and  pressure  must  be 
prevented  as  far  as  possible.  Accordingly,  there  is  no  fundamental 
or  indispensable  portion  of  an  acetylene  apparatus  which  lends  itself 
to  the  protection  of  the  patent  laws. 

Treatment  of  Acetylene  after  Generation. — The  calcium  carbide 
manufactured  to-day,  even  the  best  obtainable,  is  by  no  means  a 
chemically  pure  substance.  It  contains  a  large  number  of  impurities, 
or  foreign  bodies,  some  of  which  evolve  gas  on  treatment  with  water. 
To  a  certain  extent,  this  statement  will  always  remain  true  in  the 
future,  for  in  order  to  make  absolutely  pure  carbide  it  would  be  neces- 
sary for  the  manufacturer  to  obtain  and  employ  perfectly  pure  lime, 
carbon,  and  electrodes  in  the  electric  furnace  which  did  not  suffer 
attack  during  the  passage  of  a  powerful  current,  or  he  would  have  to 
devise  some  process  simultaneously  or  subsequently  removing  from 
his  carbide  those  impurities  which  were  derived  from  his  impure  raw 
material,  or  from  the  walls  of  his  furnace.  Besides  the  impurities 
thus  inevitably  arising  from  the  calcium  carbide  decomposed,  how- 
ever, other  impurities  may  be  added  to  the  acetylene  by  the  action 
of  a  badly  designed  generator,  or  one  working  on  a  wrong  system  of 
construction.  Therefore  it  may  be  said  at  once  that  the  crude  gas 
coming  from  the  generating  plant  is  seldom  fit  for  immediate  con- 
sumption. It  must  invariably  be  submitted  to  a  rigorous  method 
'  of  chemical  purification. 

Combining  together  what  may  be  termed  the  cajbide  impurities 
and  the  generator  impurities,  in  crude  acetylene  the  foreign  bodies 
are  partly  gaseous,  partly  liquid,  partly  solid.  They  may  render  the 
gas  dangerous  from  the  point  of  view  of  possible  explosion.  They 
may  be  harmful  to  health  if  inhaled,  injurious  to  the  fittings  and 
decorations  of  rooms,  objectional  at  the  blowpipe  orifices  by  deter- 
mining or  assisting  the  formation  of  the  solid  growths  which  dis- 
tort the  flame  and  so  reduce  its  power;  they  may  give  trouble  in  the 
pipes  by  condensing  from  the  state  of  vapour  in  the  bends  and  dips, 
or  by  depositing,  if  they  are  already  solid,  in  angles,  etc.,  and  so 
causing  stoppages. 

It  will  be  apparent  without  argument  that  a  proper  system  of 


32  MODERN  METHODS  OF  WELDING 

purification  is  one  that  is  competent  to  remove  the  carbide  impurities 
from  acetylene,  as  far  as  removal  is  desirable  or  necessary.  It  should 
not  be  necessary  to  extract  generator  impurities,  because  the  proper 
way  to  deal  with  them  is  to  prevent  their  formation.  Vapour  of 
water  almost  always  accompanies  acetylene  from  the  generator, 
this  being  due  to  the  fact  that  in  a  generator  where  the  carbide  is  in 
excess  the  temperature  tends  to  rise  until  part  of  the  water  is  vapor- 
ised and  carried  out  of  the  decomposing  chamber  before  it  has  an 
opportunity  of  reacting  with  the  excess  of  carbide.  In  large  plants 
the  extraction  of  the  moisture  may  take  place  in  two  stages.  The 
gas  from  the  generator  is  generally  passed  slowly  through  a  condenser, 
although  in  smaller  generators  it  is  often  quite  suitable  for  the  gas 
to  pass  through  the  water  of  the  generator  in  order  to  remove  the 
soluble  impurities.  The  generator  impurities  present  in  the  crudest 
acetylene  consist  of  hydrogen  and  nitrogen — i.e.,  the  main  con- 
stituents of  air;  the  various  gases — liquid  and  semisolid  bodies—- 
which are  produced  by  the  polymerising  and  decomposing  action  of 
heat  upon  the  carbide,  water,  and  acetylene  in  the  apparatus ;  and, 
wherever  the  carbide  is  in  excess  in  the  generator,  some  lime  in  the 
form  of  very  fine  dust.  This  lime  dust,  which  is  calcium  oxide  or 
hydroxide,  carried  forward  by  the  stream  of  gas  in  extremely  fine 
subdivision,  is  liable  to  be  produced  whenever  water  acts  rapidly 
upon  an  excess  of  calcium  carbide.  It  occasionally  appears  in  the 
alternative  form  of  froth  in  the  pipes  leading  directly  from  the 
generating  chamber.  This  froth  is  hard  to  break  up. 

A  purifying  system  must  remove  generator  impurities,  unless  the 
generator  is  so  perfect  that  it  does  not  give  them  off.  With  the 
exception  of  the  gases  which  are  permanent  at  atmospheric  pressure 
— hydrogen,  carbon  monoxide,  nitrogen,  and  oxygen — which,  once 
produced,  must  remain  in  the  acetylene,  extraction  of  these  im- 
purities is  quite  simple.  The  dust  or  froth  of  lime  will  be  removed 
in  the  washer  where  the  acetylene  bubbles  through  water.  The 
dust  itself  can  be  extracted  by  merely  filtering  the  gas  through 
cotton -wool,  felt,  or  the  like.  The  least  volatile  liquid  impurities 
can  be  removed  partly  in  the  condenser,  partly  in  the  washer,  partly 
by  a  mechanical  dry-scrubbing  action  of  the  solid  purifying  materials 
in  the  chemical  purifier.  To  some  extent  the  more  volatile  liquid 
bodies  may  be  removed  similarly. 

Carbide  Impurities. — Neglecting  very  minute  amounts  of  carbon 
monoxide  and  hydrogen  as  being  insignificant  from  the  practical 
point  of  view,  the  carbide  impurities  of  the  gas  fall  into  three  main 
categories :  those  containing  sulphur,  those  containing  silicon,  those 


ACETYLENE  33 

containing  gaseous  ammonia.  The  phosphorus  in  the  gas  becomes 
calcium  phosphide  in  the  calcium  carbide  which  is  attacked  by 
water,  and  yields  phosphuretted  hydrogen  (or  phosphine).  The 
calcium  phosphide,  in  its  turn,  is  produced  in  the  electric  furnace 
by  the  action  of  the  coke  upon  the  phosphorus  in  phosphatic  lime. 
The  sulphur  in  the  gas  comes  from  aluminium  sulphide  in  the  carbide. 
Even  in  the  absence  of  aluminium  compounds,  sulphuretted  hydro- 
gen may  be  found  in  the  gas  of  an  acetylene  generator.  In  the  gas 
itself  the  ammonia  exists  as  such,  the  phosphorus  mainly  as  phos- 
phine. The  sulphur  is  present  partly  as  sulphuretted  hydrogen, 
partly  as  organic  compounds  analogous,  in  all  probability,  to  those 
of  phosphorus.  Ammonia  and  sulphuretted  hydrogen  are  both 
soluble  in  water,  the  latter  more  particularly  in  limewater  of  an 
active  acetylene  generator,  while  all  other  bodies  referred  to  are 
completely  insoluble.  Therefore  a  proper  washing  of  crude  gas 
in  the  water  should  suffice  to  remove  all  ammonia  and  sulphuretted 
hydrogen  from  the  acetylene. 

When    acetylene    was   first   introduced    on    commercial   lines, 
the   generator   manufacturers   began    to    attack   the   problem    of 
purification  in  a  perfectly  empirical  way,  either  employing  some 
purely  mechanical  scrubber,  filled  with  moist  or  dry  porous  material, 
or  perhaps  coke  or  the  like,  wetted  with  dilute  acid.     At  first  sight 
it  might  appear  that  the  methods  of  treating  coal-gas  would  suit 
acetylene,  as  the  latter  contains  two  of  the  impurities,  sulphuretted 
hydrogen  and  ammonia.     Setting  on  one  side,  as  worthy  of  atten- 
tion, certain  compositions  offered  as  acetylene-purifying  materials, 
whose  constitutions  have  not  been  developed,  and  whose  action 
has  not  been  certified  by  respectable  authority,  there  are  now  three 
principal  chemical  reagents  in  regular  use.     These  are  chromic  acid, 
cuprous  chloride,  and  bleaching  powder.     Chromic  acid  is  employed 
in  the  form  of  solution  acidified  with  acetic  acid.     In  order  to  obtain 
the  advantages  attendant  upon  the  use  of  a  solid  purifying  material, 
this  is  absorbed  in  that  highly  porous  and  inert  silica  known  as 
infusorial  earth  or  "  kieselguhr."     This  substance  was  first  recom- 
mended by  Ullmann,  and  is  termed  commercially  "  heratol."    As 
sold,  it  contains  about  136  grammes  of  chromic  acid  per  kilogramme. 

Cuprous  chloride  is  used  as  a  solution  in  strong  hydrochloric 
acid,  mixed  ferric  chloride,  similarly  absorbed  in  "  kieselg  hr." 
From  the  name  of  its  proposer,  this  composition  is  called  "franko- 
line."  It  will  be  observed  that  both  heratol  and  frankoline  are 
powerfully  acid,  whence  it  follows  that  they  are  capable  of  extract- 
ing any  ammonia  that  may  enter  the  purifier.  But  this  material 


34  MODERN  METHODS  OF  WELDING 

should  be  in  an  earthen  vessel.  Heratol  changes  somewhat  in  colour 
as  it  becomes  spent,  its  original  tint,  due  to  the  chromic  acid,  altering 
to  a  dirty  green,  characteristic  of  the  reduced  state  of  the  chromium. 

Frankoline  has  been  asserted  to  be  capable  of  regeneration  or 
revivification — i.e.,  when  spent  it  may  be  rendered  fit  for  further 
service  by  being  exposed  to  the  air  for  a  time,  as  is  done  with  gas 
oxide. 

Of  all  these  materials,  heratol  is  the  completest  purifier  of 
acetylene,  removing  phosphorus  and  sulphur  most  rapidly  and 
thoroughly,  and  not  appreciably  diminishing  in  speed  or  efficiency 
until  its  chromic  acid  is  practically  used  up.  On  the  other  hand, 
heratol  does  not  act  on  pure  acetylene,  so  that  purifiers  containing 
it  should  be  small  in  size,  and  frequently  recharged. 

Frankoline  is  very  efficacious  as  regards  phosphorus,  but  it  does 
not  extract  sulphur.  The  purifying  materials  mentioned  may  be 
valued  by  their  price,  proper  allowance  being  made  for  the  quantity 
of  gas  purified  per  unit  weight  of  substance  taken.  The  annexed 
table  shows  approximately : 

(1)  The  number  of  litres  of   gas  purified  by  1  kilogramme  of 
the  substance,  and 

(2)  The  number  of  cubic  feet  purified  per  pound. 

Litres  per  Cubic  Feet 

Kilogramme.  per  Pound. 
Heratol           ..         ..        5,000  80 

Frankoline      ..         ..        9,000  144 

Puratylene      ..          ..         1,000  156 

Opinions  differ  as  to  the  maximum  volume  of  acetylene  which  a 
certain  variety  of  purifying  material  will  treat.  If  1  pound  of  a 
certain  substance  will  purify  200  cubic  feet  of  normal  crude  acetylene, 
that  weight  is  sufficient  to  treat  the  gas  evolved  from  40  pounds 
of  carbide,  but  it  will  only  do  so  provided  it  is  so  disposed  in  the 
purifier  that  the  gas  does  not  pass  through  it  at  too  high  a  speed 
that  it  is  capable  of  complete  exhaustion. 

Purifiers  charged  with  heratol  are  stated,  however,  to  admit  of  a 
more  rapid  flow  of  the  gas  than  is  the  case  with  other  materials. 
The  ordinary  allowance  is  1  pound  of  heratol  for  every  cubic  foot 
per  hour  of  acetylene  passing,  with  a  minimum  charge  of  7  pounds 
of  the  material.  As  the  quantity  of  the  material  is  increased,  the 
flow  of  the  gas  per  hour  may  be  proportionately  increased — e.g., 
a  purifier  charged  with  133  pounds  of  heratol  should  purify  144 
cubic  feet  of  acetylene  per  hour. 


CHAPTER  VII 
OXYGEN  CYLINDERS 

THE  rapid  and  extensive  developments  of  the  oxy-acetylene  process 
in  recent  times  has  led,  of  course,  to  a  corresponding  growth  in  the 
handling  and  use  of  oxygen  cylinders.  If  simple  and  indispensable 
precautions  are  followed  in  manipulating  the  cylinders  and  utilising 
the  gas  they  contain,  no  real  danger  is  present;  but  many  welders 
are  entirely  ignorant  of  the  care  required,  and  the  author  proposes 
therefore  to  mention  a  few  principal  points  in  the  construction  and 
handling  of  these  cylinders. 

The  manufacture,  transport,  and  utilisation  of  cylinders  of  com- 
pressed gases  were  investigated  by  a  Government  Committee  in 
1895,  and,  although  their  recommendations  have  not  been  converted 
into  law,  they  form  the  basis  for  the  manufacture  of  cylinders  and 
the  regulation  of  the  gas-cylinder  trade.  The  oxygen  cylinders 
usually  employed  in  oxy-acetylene  welding  contain  from  100  to  200 
cubic  feet  of  gas  under  a  pressure  of  120  atmospheres,  or  1, 800  pounds 
per  square  inch.  The  cylinders  containing  100  cubic  feet  are  most 
used,  the  approximate  dimensions  of  this  size  being  7  inches 
diameter  and  49  inches  over-all  length,  including  valve.  The  cylinder 
weighs  approximately  1  cwt.  The  majority  of  the  cylinders  are 
made  of  seamless  steel,  and  the  method  of  manufacture  is  of  interest. 
A  flat  steel  slab,  about  f  inch  thick,  is  raised  to  a  red  heat,  and  sub- 
jected to  three  hot  drawing- through  processes.  The  cylinder  is 
next  annealed,  and  then  pickled  in  acid  to  remove  the  scale.  After 
this  it  is  subjected  to  about  six  cold  drawings,  so  as  to  produce  the 
right  shape,  length,  and  thickness.  The  bottom  of  the  cylinder  is 
hemispherical  and  the  open  end  is  swaged  down,  after  previously 
upsetting  the  end  of  the  tube  so  as  to  form  the  neck,  which,  in  turn, 
is  screwed  to  receive  the  cylinder's  valve. 

After  manufacture,  the  cylinders  are  annealed  by  the  manu- 
facturers, and  reannealed,  valved,  and  tested  by  the  compressing 
firm.  The  cylinders  are  reannealed  every  third  or  fourth  year,  and 
re  tested  every  one  or  two  years.  They  are  stamped  on  the  neck, 
so  that  at  any  time  in  their  history  they  can  be  traced.  The  most 
important  marks  are  the  annealing  and  test-mark,  giving  the  date 

35 


36  MODERN  METHODS  OF  WELDING 

of  the  last  testing  and  annealing.  A  useful  mark  on  the  cylinder 
is  that  of  its  capacity  or  internal  volume.  A  foot  is  sometimes 
shrunk  on  the  base  of  the  cylinder.  This  enables  it  to  be  placed 
in  an  upright  position,  and  avoids  sudden  shocks  in  manipulation. 
Sectional  views  through  typical  oxygen  cylinders  are  shown  in 
Fig.  9.  The  cap  is  shown  separately. 

With  regard  to  the  testing  of  cylinders,  ordinary  tensile,  elonga- 
tion, and  bending  tests  can  only  be  carried  out  on  finished  cylinders 
by  destroying  them.  It*  is  useful  to  carry  out  tests  to  destruction 
on  about  2  per  cent,  of  the  cylinders  made  at  one  time  to  any  given 
specification.  Tests  for  cylinders  which  are  to  be  put  into  use  are 
of  two  kinds : 

(1)  The  Hydraulic  Test. — The  cylinder  is  subjected  to  an  hydraulic 
pressure,    usually   about   double   the   intended   working   pressure. 
If  a  cylinder  stands  this  test,  it  should  be  perfectly  safe  for  the  work- 
ing pressure.     The  hydraulic  test  gives  no  information  as  to  whether 
the  cylinder  is  annealed  or  not  or  whether  the  steel  is  ductile. 

(2)  The  Stretch  Test. — It  being  necessary  to  examine  whether 
the  cylinder  has  .permanently  stretched  during  the  hydraulic  test, 
compressing  firms  have  introduced  an  easily  applied  and  sensitive 
test  called  the  stretch  test.     During  the  hydraulic  test  the  cylinder 
is  placed  in  a  vessel,  which  forms  a  water-jacket.     A  pipe  and  glass 
tube  communicate  with  this  jacket.     If  there  is  any  expansion  of  the 
cylinder  during  the  hydraulic  test  water  is  driven  out  of  the  jacket 
and  rises  in  the  glass  tube.     Oxygen  cylinders  always  contain  a 
certain  amount  of  water  which  it  is  impossible  to  eliminate,  and 
which   accumulates   during    successive   fillings,    finally   occupying 
several  cubic  inches.     It  is  therefore  necessary  carefully  to  drive 
out  the  water  contained  in  a  full  cylinder  before  screwing  the  pres- 
sure-reducing valve  in  position.     In  this  manner  the  life  of  the 
cylinder  is  increased,  and  the  difficulties  encountered  when  using 
large  quantities  of  oxygen  (as,  for  example,  in  cutting)  are  removed 
or  reduced. 

Cylinders  of  compressed  oxygen  can  be  manipulated  without  any 
very  special  precautions.  For  use  they  are  placed,  according  to 
shape,  upright  or  lying  down.  Carefully  avoid  letting  them  fall. 
Such  accidents  do  not  affect  cylinders,  but  may  injure  the  welders, 
and  in  many  cases  damage  the  reducing  valve.  The  cock  or  valve 
J£  the  delicate  part  of  the  cylinder.  The  welder  has  only,  in  theory, 
do  open  and  close  the  valve  at  the  beginning  and  the  end  of  the 
work.  This  operation,  so  simple  in  itself,  requires  certain  precau- 
tions. Often  on  the  arrival  of  the  cylinder  the  valve  is  hard  to 


OXYGEN  CYLINDERS  37 

open.  The  operator  should  make  sure  of  its  working  before  placing 
the  reducing  valve  in  position,  so  that  any  powdered  oxide  or  other 
dust  is  blown  away.  The  oxygen  on  escaping  into  the  air  produces 
a  violent  hissing.  The  valve  should  be  opened  and  closed  alternately 
two  or  three  times.  The  slightest  escape  can  be  detected  by  the 
ear.  The  reducing  valve  should  now  be  fixed,  care  being  taken 
to  see  that  the  screw  on  the  valve  is  put  in  square  to  the  thread  of 
the  cylinder,  so  as  to  avoid  damaging  the  thread.  Screw  down 
tightly  with  the  spanner  supplied  with  the  cylinder.  Then  open 
the  tap  on  the  reducing  valve  where  the  rubber  pipe  fits  on,  and  turn 
on  gently  the  gas  at  the  cylinder  tap,  and  test  if  there  is  any  leakage 
at  the  cylinder  or  valve.  If  there  is  an  escape,  which  may  be  shown 
by  the  pointer  on  the  gauge  rising  after  the  valve  of  the  cylinder  has 
been  closed,  try  to  screw  the  valve  tighter  without  overdoing  it, 
because  it  will  be  difficult  to  reopen  after.  If  the  leak  still  con- 
tinues, remove  the  reducing  valve,  and  open  the  cylinder  valve 
briskly  two  or  three  times. 

No  grease,  oil,  soap,  or  any  fatty  matter  must  be  used,  as 
oxygen  under  pressure  has  an  oxidising  action  on  all  these  articles. 
This  causes  heat  to  be  produced,  which  may  start  combustion,  and 
the  conflagration  may  spread  to  the  ebonite  parts  of  the  valve  and 
destroy  them.  The  oxygen  then  escapes  in  large  quantities  from 
the  cylinder,  thus  tending  to  produce  a  brisk  combustion  by  con- 
tact with  a  lighted  body.  The  results  may  be  serious.  In  case  the 
leak  is  considerable  and  it  is  possible  to  stop  it  by  ordinary  methods, 
the  cylinder  should  be  returned  to  the  manufacturers,  with  a  label 
attached,  "Valve  faulty,"  so  that  the  manufacturers  can  proceed 
to  repair  it  before  refilling. 

There  are  cases  of  freezing  of  the  reducing  valve  by  the  solidifica- 
tion of  water -vapour.  Particular  warning  must  be  given  against 
melting  the  ice  by  heating  with  the  flame  of  the  blowpipe.  This 
is  a  bad  practice,  and  may  lead  to  accidents.  The  only  thing  is  to 
use  warm  water.  In  order  to  avoid  excessive  expansion  of  the  gas, 
and  the  resulting  increase  in  pressure,  the  cylinders  should  always 
be  kept  away  from  a  warm  place.  Avoid  placing  them  in  the  sun 
or  near  fires.  After  emptying,  the  cylinders  should  be  immediately 
returned  to  the  company  to  be  refilled.  They  generally  belong  to 
the  manufacturers,  but  one  can  purchase  one's  own.  Oxygen 
cylinders  are  carried  on  the  railways  at  class  2  rates  by  goods 
train,  and  empties  returned  at  reduced  rates.  All  sent  by  rail 
must  be  fitted  with  covers,  as  specified  by  the  Railway  Clearing 
House. 


38  MODERN  METHODS  OF  WELDING 

Although  much  literature  on  oxy-acetylene  welding  and  cutting 
has  appeared  in  recent  years,  there  has  not  been  any  of  a  general 
character  in  which  concise  and  comprehensive  regulations  have  been 
given  to  blowpipe  operators. 

One  frequently  comes  across  cases  of  trained  and  efficient  welders 
who  are  incurring  daily  risks  at  their  work  simply  because  many 
important  precautions  and  regulations  are  unknown  to  them.  It 
is  safe  to  say  far  more  welding  accidents  occur  through  ignorance 
than  through  wilful  neglect  of  ordinary  safeguards.  Only  a  very 
small  proportion  of  operators  have  had  the  advantage  of  training  at  a 
welding  school.  No  opportunity  should  be  lost  of  placing  regulations 
bearing  on  their  own  security  before  the  large  number  of  men  and 
women  operators  now  employed  throughout  the  country.  I  append, 
therefore,  the  necessary  regulations,  and  I  impress  on  all  operators 
to  carry  them  out  for  the  safeguarding  of  themselves  and  others. 

Regulations,  Precautions,  and  Safeguards. 

(1)  In  placing  contracts  for  oxygen  supplies,  a  guarantee  from 
the  supplier  should  be  obtained,  to  the  effect  that  oxygen  will  only 
be  delivered  in  cylinders  which  have  been  made,  annealed,  tested, 
and  filled  strictly  in  accordance  with  the  recommendations  of  the 
British  Government  Departmental  Committee  of  1896. 

The  British  railways  and  all  the  responsible  road  and  water 
carriers  require  these  conditions  to  be  complied  with. 

(2)  A  guarantee  should  be  also  obtained  to  the  effect  that  the 
oxygen  supplied  will  be  not  less  than  98-5  per  cent,  quality. 

(3)  See  that  all  cylinders  supplied  with  oxygen  are  painted  black 
and  fitted  with  right-hand  valves ;  never  attempt  to  alter  the  colour 
of  the  cylinder  or  the  screwed  thread  of  the  valve  connections. 

(4)  See  that  cylinders  are  not  exposed  to  excessive  heat. 

(5)  Oxygen  cylinders  should  not  be  exposed  to  temperature 
exceeding  1,000°  F. 

(6)  Take  care  not  to  lay  hot  welded  or  cut  material  on  or  along- 
side oxygen  cylinders ;  and  great  care  must  be  taken  never  to  allow 
the  blowpipe  flame  or  the  heat  from  the  same  to  impinge  on  the 
oxygen  cylinder. 

(7)  Carefully  avoid  the  use  of  oil  or  grease,  or  lubricant  in  any 
form,  upon  the  cylinder  valves  or  fittings,  and  keep  same  dry  and 
free  from  grit. 

(8)  Never  use  keys  of  long  leverage  to  close  cylinder  valve; 
they  give  under  power,  which  is  injurious  to  the  valves,  and  fre- 


OXYGEN  CYLINDERS 


39 


quently  results  in  broken  spindles.  If  the  valve  leaks  when  closed 
with  ordinary  lever  key,  it  is  often  due  to  grit.  To  remove  this, 
open  the  valve  slowly,  and  then  close  it  sharply. 

(9)  After    disconnecting    a    cylinder    before    it    is    empty,    it 
is  desirable   to   test  for    leakage 

by  pouring  some  water  into  the 
valve  socket.  If  no  bubbles  ap- 
pear in  the  water,  it  proves  that 
the  valve  is  gas-tight.  The  valve 
gland  can  be  tested  in  the  same 
way  at  any  time  that  the  valve 
is  open,  and  a  regulator  at- 
tached, by  pouring  water  into 
the  recessed  part  of  the  gland- 
nut  round  the  spindle.  The 
gland-nut  must  be  tightened  up 
if  necessary  to  prevent  leakage. 

(10)  See   that  all  socket  and 
nipple  ends  are  in  good  order  and 
free  from  grit  before  fixing  regu- 
lators or  other  fittings  by  screwing 
up  the  fly-nut  "  hand  tight." 

(11)  Never  open  the  cylinder 
valve  suddenly  when  the  regulator 
is   fixed.      The  valve   should   be 
opened  by  tapping  the  key  gently 
with  the  hand. 

(12)  Store     cylinders    under 
cover   in   an   outhouse,    or    in   a 
portion    of    the    premises    most 
remote   from  any   source  of  fire 
risk.     Avoid  as  much  as  possible 
exposing  cylinders  to  conditions 
which   promote  oxidisation,    and 
return    empty    cylinders    to    the 
oxygen    factory    as    quickly    as 

possible.  Cylinders  should  be  returned  with  a  label  bearing 
the  customer's  name,  so  that  they  may  be  identified  and  credited 
to  him  in  the  oxygen  factory. 


FIG.  9. — SECTION  OF  AN  OXYGEN, 
CYLINDER. 


CHAPTER  VIII 
ACETYLENE  GENERATORS 

General  Construction. — Acetylene  generators  may  be  divided 
into  several  classes.  For  the  purpose  of  description  three  types 
will  be  taken — namely,  water-to-carbide,  carbide-to-water,  and  the 
dipping  or  contact  generators.  We  will  describe  each  one  by  itself, 
and  state  the  advantages  and  disadvantages  as  they  arise. 

Most  people,  when  taking  up  oxy-acetylene  welding,  decide  to 
purchase  a  small  portable  generator.  This  is  a  mistake.  Such  a 
generator  is  only  intended  for  occasional  use.  It  frequently 
happens,  therefore,  that  the  purchaser  finds  after  a  few  weeks  that 
the  generator  is  not  large  enough,  and  he  has  to  purchase  a  larger 
one.  It  is  very  much  better  to  have  a  large  one  at  first.  The  first 
,  cost  may  be  higher,  but  the  advantages  are  many,  and  the  saving  in 
gas  would  pay  for  the  extra  cost  in  a  few  months. 

Generators  should  be  well  designed  by  competent  men  who  have 
had  years  of  experience,  and  everything  should  be  carefully  thought 
out  and  well  constructed,  somewhat  on  the  following  lines  : 

(1)  Generating  casing  should  be  made  of  strong  steel  sheets,  and, 
after  manufacture,  galvanised. 

(2)  The  tubes  and  fittings  all  galvanised. 

(3)  Two  or  more  generating  chambers. 

(4)  Generator  capable  of  recharging  while  working. 

(5)  Quite  automatic. 

(6)  Capable  of  taking  any  over  generation. 

(7)  Washer  to  absorb  the  ammonia  and  sulphurous  acid. 

(8)  Purifier  with  chemical  composition  for  the  removal  of  phos- 
phorus and  other  impurities. 

(9)  Large  outlet  and  inlet  tubes,  so  as  not  to  throttle  the  gas. 

(10)  No  copper  should  be  used  on  any  part  of  the  generator. 
The  production  of  acetylene  by  the  action  of  water  on  calcium 

of  carbide  is,  chemically,  one  of  the  simplest  of  reactions.  But  in 
practice  it  is  not  so  simple.  The  two  chief  difficulties  in  the  pro- 
duction of  acetylene  are  heating  and  excess  production.  Water 
consists  of  hydrogen  and  oxygen,  the  dissociation  of  which  takes 

49 


ACETYLENE  GENERATORS  41 

place  with  the  absorption  of  heat.  On  the  other  hand,  the  oxygen 
liberated  combines  with  calcium  carbide  and  produces  the  action 
more  heat  than  is  absorbed  by  the  above  reaction.  The  heat  liber- 
ated is  226  calories  or  900  B.T.U.  per  pound  of  carbide — that  is  to 
say,  1  pound  of  carbide  would  raise  1  gallon  of  water  from  0°  to  50°  C. 
No  device  or  arrangement  can  alter  this  amount  of  heat  liberated ; 
but  the  temperature  of  the  mass  altered  will  not  go  beyond  the 
temperature  of  boiling  water.  This  result  is  caused  in  two  ways: 
(1)  The  water  vaporises  and  acts  with  the  carbide,  thus  supple- 
menting the  heat  of  decomposition;  (2)  under  the  influence  of  heat 
the  lime  gives  up  the  water,  reaction  continues,  and  if  there  is  no 
external  cooling  the  temperature  rises.  The  generation  of  acetylene 
at  a  high  temperature  is  detrimental,  and  causes  polymerisation. 
This  is  one  reason  why  manufacturers  often  put  the  generating 
chambers  inside  the  tanks,  so  as  to  have  the  water  all  round  them, 
and  also  to  have  the  outlet  pipes  from  the  generating  chambers 
turned  down  from  the  top,  so  that  the  gas  is  passed  through  the 
water  cooled  and  washed. 

Polymerisation,  as  stated  previously,  takes  place  owing  to  too 
rapid  generation,  which  results  in  excessive  heat  to  a  temperature 
of  130°  F.  and  causes  the  lime  or  spent  carbide  to  turn  yellow  in  the 
carbide  trays,  being  in  the  form  of  a  tarry  substance. 

Carbide  gives  up  sulphide  on  the  action  of  heat;  and  the  water 
decomposes  into  hydrogen  sulphide  and  organic  sulphur  compounds, 
which  are  very  detrimental  to  acetylene.  The  unpleasant  odours  of 
sulphur  dioxide  are  given  off  on  the  heating  of  the  gas. 

No  generator  produces  the  proper  proportion  of  gas  consumed. 
The  production,  therefore,  is  either  in  excess  or  deficient.  Produc- 
tion being  in  advance,  the  sudden  stoppage  of  consumption  cannot 
possibly  correspond  to  the  above  arrest  of  the  reaction. 

It  is  important  to  note  that  any  particular  generator-heating  and 
after-generation  are  in  direct  relation  to  the  delivery.  It  is  there- 
fore impossible  to  formulate  rules  on  this  point  without  taking  into 
account  the  delivery.  The  heating  should  never  exceed  a  tempera- 
ture of  130°  C.  The  generator  bell  should  be  large  enough  to  take 
all  the  after-generation  in  the  case  of  stoppage.  A  well-designed 
and  constructed  generator  needs  the  minimum  of  attention.  It  is 
entirely  automatic,  only  gives  gas  as  required,  is  strong,  and  will 
last  for  a  number  of  years. 

The  characteristic  point  in  every  generator  for  welding  is  its 
flexibility.  It  should  adapt  itself  to  fluctuating  employment — 
that  is,  should  rise  to  the  maximum  and  minimum  yield  without 


42  MODERN  METHODS  OF  WELDING 

delay,  without  heating,  without  jerks.     This  refers  to  automatic 
generators  only. 

Non-automatic  generators  are  usually  of  large  dimensions,  in 
which  the  gas  is  made  in  large  quantities  in  advance  and  stored  in  a 
gasometer  of  from  50  to  500  cubic  feet.  This  method  is  the  most 
practical,  most  sure,  and  most  economical  by  a  long  way,  but  the 
initial  cost  is  high. 


FIG.  10. — 10-CwT.  CARBIDE-TO-WATER  GENERATOR. 

Fig.  10  is  a  photograph  of  a  large  generating  plant,  comprising 
generator,  condenser,  washer,  gasometer,  and  purifier.  It  is 
worked  on  the  usual  principle. 

Figs.  11  and  12  are  carbide-to-water  type  generators,  medium- 
pressure  type,  which  makes  it  possible  for  the  storage  of  the 
generated  gas,  with  its  accompanying  advantage  of  absolute 
volumetric  control.  The  gasometer  obviates  the  variation  of  gas 


ACETYLENE  GENERATORS 


43 


pressure  that  is  inherent  in  the  pressure  generator.  No  regulating 
or  reducing  device  is  necessary,  as  the  acetylene  is  generated  at  the 
pressure  required  for  use.  The  possibility  of  loss  of  gas  through 
leakage  in  the  line  and  connections  is  practically  eliminated  with 
the  low-pressure  system.  The  gas  bell  provides  storage  for  gas  and 
effectively  guards  against  the  loss  due  to  after-generation  inherent 
in  other  systems. 

Control  of  the  feed 
mechanism  is  accomplished 
through  the  rise  and  fall  of 
the  gas  bell,  and  with  abso- 
lute gas-pressure.  The  move- 
ment of  the  gas  bell  gives 
a  dual  motor  control — first, 
through  a  brake;  second, 
through  a  position  jaw 
clutch.  Special  provision  is 
made  for  shutting  off  the 
motor  feed  when  the  gas 
bell  is  in  its  lowest  position. 

Operation  of  the  genera- 
tor is  effected  by  a  small 
but  efficient  weight-driven 
motor,  which  automatically 
starts  and  stops  to  supply 
the  amount  of  gas  being 
used.  The  motor  weights 
always  lower  approximately 
the  same  distance  for  each 
pound  of  carbide  used,  and 
constitutes  a  reliable  indica- 
tion of  the  amount  of  carbide 
remaining  in  the  machine  at 
any  time.  By  the  use  of 

positive  forced  feed,  it  is  impossible  for  more  than  the  proper 
quantity  of  carbide  to  be  fed  in  the  water.  In  securing  cool, 
and  hence  efficient,  generation,  it  is  necessary  to  have  not  less 
than  1  gallon  of  water  capacity  per  pound  of  carbide  charge.  It 
is  impossible  for  the  temperature  of  the  gas  to  rise  above  the 
boiling-point  of  water,  the  acetylene  bubbling  through  the  water, 
free  from  some  of  the  impurities.  By  the  time  the  gas  is  ready 
to  leave  the  surface  outlet  its  temperature  does  not  exceed  that 


FIG.  11. — 50  POUNDS  CARBIDE  CAPACITY, 

USING  1J  POUNDS  CARBIDE. 

Height,  62  inches;  diameter,  24  inches; 

weight,  450  pounds. 


44 


MODERN  METHODS  OF  WELDING 


of  the  air  by  more  than  a  few  degrees.     These  conditions  permit 

a  yield  of  pure  gas. 

A  complete  and  efficient  system  of  interlocking  safety  devices 

prevents  mistakes  in  operation  due  to  carelessness  or  forgetfulness 

when  charging  the  generator.     The  hydraulic  back-pressure  valve 

is  of  unique  design.  With  three 
distinct  water  seals,  it  prevents 
the  possibility  of  any  oxygen 
entering  the  generator.  The 
generator  is  equipped  with  an 
agitator  that  churns  the  resi- 
duum thoroughly,  allowing  it 
to  flow  freely  and  quickly  when 

\the  residuum  is  opened  for  re- 
charging. 

These  generators  produce 
acetylene  at  a  pressure  of  less 
than  15  pounds.  After  the 
hopper  has  been  filled  with 
carbide  (IJ-inch  mesh)  it  is  fed 
to  water  by  means  of  a  re- 
volving disc;  surrounding  this 
disc  are  little  plows,  or  scrapers, 
that  scrape  off  a  certain  quan- 
tity of  the  carbide  as  the  disc 
revolves.  The  disc  is  controlled 
by  a  governor  which  is  actuated 
by  the  gasometer.  When  the 
gasometer  reaches  a  predeter- 
mined height,  the  motor  is 
stopped  by  means  of  a  brake. 
When  the  gas  bell  recedes,  the 
motor  is  automatically  started 
by  releasing  the  brake.  The 
gas  passes  from  the  generator 
chamber  into  the  gasometer. 
From  there  it  passes  through 

the  filter,  where  physical  impurities  and  suspended  matter  are 
removed,  and  then  through  the  hydraulic  valve,  which  is  a  water  seal 
for  preventing  the  reverse  flow  of  gas  or  air.  The  gas  then  passes 
into  the  service  line.  The  filter  consists  of  a  cylindrical  shell  within 
which  felt  is  placed.  Perforated  plates  are  placed  at  the  top  and 


FIG.  12. — 100  POUNDS  CARBIDE  CAPACITY, 
USING  1£  POUNDS  CARBIDE. 

Height,  76  inches;  diameter,  30  inches; 
weight,  550  pounds.  Known  as  Davis- 
Bournonville  Pressure  Generators. 


ACETYLENE  GENERATORS  45 

bottom.  The  gas  passes  up  through  the  perforations  and  felt,  which 
collects  all  dirt,  lime,  or  portions  of  sludge  that  would  otherwise 
enter  the  service  line  with  the  gas. 

The  bell  tank  is  divided  by  the  horizontal  partition,  the  lower 
portion  of  the  tank  forming  the  seal  chamber.  The  stand  pipe 
projects  downward  into  this  chamber,  being  sealed  with  water  it 
contains.  The  function  of  the  seal  chamber  is  to  prevent  an  ex- 
cessive pressure  from  accumulating  within  the  apparatus,  and  pre- 
cludes the  possibility  of  a  backward  or  reverse  pressure  entering  the 
generator.  Should  the  pressure  of  the  gas  from  any  cause  be  in- 
creased above  the  normal  pressure,  the  seal  will  immediately  break. 
The  water  will  overflow  from  the  seal,  filling  lip,  and  release  the 
pressure. 

If  there  should  be  generated,  because  of  defective  or  broken 
apparatus  or  other  reasons,  a  larger  volume  of  gas  than  can  readily 
be  held  by  the  gas  bell,  the  bell  would  be  forced  upward.  In  order 
to  prevent  such  an  occurrence,  there  is  a  stand  pipe  arranged  with  a 
series  of  blow-off  holes.  This  stand  pipe  is  connected  to  the  vent 
pipe.  Should  the  stand  pipe  rise  above  the  level  of  the  water,  thus 
producing  a  free  passage  for  the  gas  down  the  stand  pipe  through 
the  safety  vent  pipe  to  the  outside  air,  as  soon  as  the  gas  bell  was 
relieved  of  the  excess  gas  it  would  lower  gradually  and  the  blow-off 
holes  would  be  again  under  the  water  and  the  flow  of  gas  shut  oif, 
thus  permitting  the  generator  to  resume  its  normal  working  condition. 
The  vent  valve,  the  generator  filling  valve,  and  the  residuum  gate 
are  so  arranged  that  they  can  only  be  operated  in  sequence.  The 
opening  of  the  residuum  gate  therefore  allows  the  gas  within  the 
generator  to  escape  to  the  outside  air  before  any  valve  or  opening 
from  the  generator  can  be  made  into  the  room. 


CHAPTER  IX 
OXYGEN  REGULATORS 

OXYGEN-REDUCING  valves  are  manufactured  by  various  firms,  and 
are  of  various  forms.  Some  are  very  reliable  and,  with  care,  will 
last  a  good  number  of  years.  The  reducing  valves  are  fixed  to  the 
oxygen  cylinder  by  means  of  a  union  on  the  valve.  The  screws  on 
the  union  are  standardised,  as  likewise  the  screws  on  the  top  of  the 
cylinder.  In  the  valve  of  the  cylinder  there  is  a  faced  surface 


FIG.  13. — OXYGEN  REGULATORS:  1  Two  GAUGES,  1  ONE  GAUGE,  1  No  GAUGE. 

(concave) ;  on  the  regulator  tip  is  a  convex-faced  and  ground  surface. 
In  fixing  the  regulator  tight  in  the  cylinder,  the  cylinder  spanner 
should  be  used,  and  care  taken  to  see  that  it  is  tight ;  before  turning 
the  oxygen  on,  open  the  tap  of  the  blowpipe  supply,  then  gently 
open  the  valve  on  the  cylinder  and  see  if  all  is  sound.  Turn  off  the 
blowpipe  tap.  The  regulator  must  not  leak  at  the  cylinder;  if  it 
does,  turn  off  the  oxygen  again  and  tighten  up  the  union.  Try  the 
gas  on  again.  If  still  leaking,  the  regulator  should  be  entirely 
removed,  and  the  oxygen  turned  on  two  or  three  times  to  blow  out 
any  grit  or  dust  that  may  have  accumulated  inside  the  valve. 

46 


OXYGEN  REGULATORS  47 

Then  fix  the  regulator  again,  and  test.  This  time  you  will  probably 
be  sound. 

It  is  most  important  to  note  that  there  is  great  danger  in  getting 
oil  or  grease  into  the  union  of  the  reducing  valve,  because  ignition 
may  take  place  and  cause  an  explosion,  doing  much  damage. 

There  are  three  types  of  regulators ;  one  is  shown  in  Fig.  13.  No.  1 
has  no  gauge  and,  naturally,  the  cost  is  less  owing  to  its  absence.  It 
is  not  absolutely  necessary  to  have  this  gauge.  The  regulator  works 


I 


FIG.  14. — DOUBLE  CYLINDER  CONNECTOR,  IN  WHICH  ONE  CAN  BE  USED  WHILE 
THE  OTHER  EMPTY  ONE  CAN  BE  CHANGED. 

quite  as  well  without,  but  one  cannot  tell  what  amount  of  gas  there 
is  in  the  cylinder ;  it  has  got  to  be  used  till  empty.  No.  2  is  the  same 
as  No.  1,  but  has  a  gauge  fitted,  which  registers  the  gas  in  the  cylinder. 
No.  3  is  for  high  pressure  and  is  used  for  cutting  purposes.  One 
gauge  is  for  the  pressure  which  is  regulated  by  the  tee  screw.  The 
other  indicates  the  amount  of  gas  in  the  cylinder.  All  oxygen 
cylinders  are  painted  black,  and  have  a  right-hand  thread  for  fitting 
into  the  cylinders.  These  regulators  are  suitable  for  every  class  of 
work  for  which  oxygen  and  other  compressed  gases  are  used.  They 
automatically  deliver  gas  from  the  cylinders  at  any  pressure  to  which 
they  are  set.  This  is  very  important  in  welding  and  for  the  correct 


48  MODERN  METHODS  OF  WELDING 

mixture  of.  the  gases.  They  are  substantial  in  construction,  are 
fitted  with  a  gas  expansion  device  which  obviates  ignition  risks  at  the 
valve  seat,  and  are  specially  recommended  for  use  for  all  kinds  of 
blowpipe  work  in  connection  with  oxygen  cylinders.  The  adjust- 
able screwed  socket  on  the  side  of  the  regulator  No.  1  is  graduated 
in  pounds  per  square  inch.  The  regulator  can  be  set  by  this  to 
any  desired  constant  pressure. 

No.  2  regulator  has  a  high-pressure  gauge  to  register  the  cylinder 
pressure;  but  these  pressure  gauges,  permanently  attached  to  regula- 
tors, are  a  fruitful  source  of  trouble.  They  soon  become  inaccurate 
(particularly  the  small  type  so  frequently  employed),  and,  being 
delicate  in  construction,  are  liable  to  injury  in  workshop  handling. 
The  connector  illustrated  in  Fig.  14  is  an  excellent  substitute  for  the 
pressure  gauge.  The  regulator  is  in  communication  with  the  cylin- 
ders A  and  B,  one  of  which  can  be  cut  off  when  not  in  use.  Thus, 
if  the  valve  of  the  cylinder  A  and  the  pipe  valve  a  are  open,  whilst 
the  valve  of  cylinder  B  and  the  valve  6  are  closed,  oxygen  flows 
from  cylinder  A  through  the  regulator  till  it  empties.  The  valve 
of  cylinder  A  is  then  closed  and  that  of  cylinder  B  opened.  Oxygen 
will  then  flow -to  cylinder  B,  whilst  the  empty  cylinder  A  can  be 
removed  and  replaced  by  a  full  one.  It  will  readily  be  seen  that 
a  continuous  supply  of  oxygen  can  be  maintained  by  the  employ- 
ment of  this  connector.  For  prolonged  use,  regulators  with  these 
connectors  will  be  found  more  convenient  and  more  reliable  than 
those  fitted  with  pressure  gauges. 

The  oxygen  should  be  opened  as  slowly  as  possible  on  to  the 
regulator,  and  the  regulating  screw  should  be  fully  open.  This 
avoids  the  heating  by  quick  compression.  This  is  important  for  the 
safety  of  the  welder,  and  preserves  the  regulator  in  good  working 
order,  because  sudden  pressure  on  the  diaphragm  of  the  regulator 
produces  derangement  and  often  puts  it  out  of  order  through  the 
diaphragm  splitting.  Regulation  of  the  pressure  should  be  secured 
by  the  regulating  screw  until  the  pressure  is  that  stamped  on  the 
blowpipe  to  be  used,  and  the  outlet  valve  should  be  full  open. 


CHAPTER  X 

REGULATIONS 

Regulations,  Precautions,  and  Safeguards  for  Oxy- Acetylene  Weld- 
ing and  Cutting. — There  has  been  much  literature  on  oxy-acetylene 
welding  and  cutting  in  the  past,  but  little  has  been  said  as  to  the 
precautions  necessary.  All  students  and  others  interested  in  the  oxy- 
acetylene  welding  and  cutting  should  study  these  regulations  very 
closely.  One  frequently  conies  across  cases  of  trained  and  efficient 
welders  who  are  incurring  daily  risks  at  their  work  simply  because 
many  important  precautions  and  regulations  are  unknown  to  them. 
It  is  safe  to  say  that  far  more  welding  accidents  occur  through  ignor- 
ance than  wilful  neglect  of  ordinary  safeguards. 

The  general  regulations  which  it  is  necessary  to  observe  in 
connection  with  oxygen  cylinders  have  been  given  above.  I  now 
add  similar  regulations  with  regard  to  carbide  and  to  acetylene 
generators. 

Carbide. 

( 1 )  Carbide  must  be  stored  in  iron  or  steel  vessels,  hermetically 
sealed. 

(2)  The  vessels  should  be  kept  in  a  dry  and  well-ventilated  place. 

(3)  No  artificial  light  capable  of  igniting  inflammable  vapour 
should  be  employed  near  these  vessels  nor  in  any  room  where  carbide 
is  stored. 

(4)  Carbide  can  only  be  stored  without  a  licence  in  a  quantity 
not  exceeding  28  pounds. 

(5)  If  it  is  desired  to  store  larger  quantities  a  licence  must  be 
obtained  from  the  local  authorities. 

(6)  Carbide  should  be  of  a  quality  to  yield  not  less  than  4-8  cubic 
feet  of  acetylene  per  pound. 

Fig.  15  shows  an  airtight  carbide  chamber;  it  holds  2  cwt. 

Acetylene  Generators. 

(1)  See  that  the  generator  is  of  ample  capacity  for  the  continuous 
production,  without  heating,  of  the  maximum  quantity  of  acetylene 
required,  and  that  it  complies  with  all  official  recommendations. 

49  4. 


50  MODERN  METHODS  OF  WELDING 

(2)  See  that,  whether  the  system  employed  be  automatic  or  non- 
automatic,  the  holder  is  of  sufficient  capacity  to  obviate  any  loss  of 
gas  due  to  production  when  the  supply  to  the  blowpipe  is  cut  off. 

(3)  See  that  the  design  precludes  any  appreciable  admission  of 
air  to  the  apparatus  in  the  charging  with  carbide. 

(4)  See  that  the  limit  of  pressure  in  any  part  of  the  apparatus 
does  not  exceed  250  inches  of  water. 

(5)  See  that  the  size  of  the  pipes  conveying  the  gas  is  propor- 
tioned to  the  maximum  rate  of  generation. 


FIG.  15. — AIRTIGHT  CARBIDE  CHAMBER. 

(6)  See  that  it  is  impossible  to  seal  hermetically  the  generating 
apparatus. 

(7)  See  that  no  copper  fittings  are  employed  in  connection  with 
the  acetylene  apparatus. 

(8)  See  that  all  back-pressure  valves  are  in  working  order  as  per 
regulations. 

(9)  Charge  the  apparatus  with  carbide,  if  possible,  only  by  day, 
and  do  not  use  small-grained  carbide. 

(10)  Keep  the  apparatus  clean  and  in  good  order,  and  carefully 
remove  all  sludge  from  the  generator  before  recharging  with  carbide. 

(11)  Do  not  use  naked  lights  in  the  vicinity  of  the  acetylene 
apparatus. 

(12)  In  frosty  weather  never  use  a  stove  in  the  vicinity  of  the 
acetylene  generator.     To  prevent  freezing  of  water,  it  is  best  to 
employ  a  steam  or  hot-water  coil. 


REGULATIONS  51 

(13)  Employ   suitable   purifying  material  and  recharge  after 
1 10  cubic  feet  per  pound  of  purifying  material  have  passed  through 
it;  test  occasionally  the  acetylene  issuing  from  the  blowpipe  with 
a  piece  of  nitrate  of  silver  paper.     If  this  is  at  all  discoloured,  it 
indicates  that  the  purifier  requires  to  be  recharged. 

(14)  See  that,  in  all  cases  where  an  acetylene  generator  is  em- 
ployed, an  hydraulic  back-pressure  valve  is  employed  between  it 
and  every  blowpipe  in  use,  and  that  it  is  properly  filled  with  water. 
The  small  drain  tap  should  be  opened  after  filling,  any  excess  of 
water  being  drained  off.     The  hydraulic  valve  must  be  tested  every 
day  in  this  way  before  being  used. 

(15)  If,  through  a  back-fire  or  other  cause,  water  is  discharged 
from  the  vent  pipe,  always  refill  the  chamber,  and  see  that  the  small 
drip  tap  is  afterwards  opened  to  draw  off  any  excess  of  water. 

(16)  The  hydraulic  back-pressure  valve  should  be  dismantled 
at  regular  intervals  and  cleaned  out,  to  make  sure  that  the  vent  pipe 
and  passages  are  clear. 


CHAPTER   XI 
BLOWPIPES 

BLOWPIPES  intended  for  the  autogenous  welding  of  metals,  which 
employ  oxygen  and  acetylene  as  the  gases,  are  manufactured  instru- 
ments, with  the  same  accuracy  as  a  watch ;  and  they  must  be  used 
as  such  with  care.  They  are  light  and  easy  to  handle,  and  are  made 
with  great  skill  so  as  to  allow  the  correct  proportions  of  acetylene 
and  oxygen,  in  specified  measured  volumes,  at  a  fixed  velocity. 


Section  of  Fouche  blowpipe 


FIG.  16. — FOUCHE  BLOWPIPE,  SECTION  AND  ELEVATION. 


according  to  the  size  of  the  blowpipe.  Their  length  and  weight 
vary,  as  does  their  size,  ranging  from  a  consumption  of  1-75  of  acety- 
lene to  100  cubic  feet  per  hour. 

The  consumption  of  acetylene  should  be  about  1  to  1  -3  of  oxygen. 
The  necessary  conditions  are  much  more  difficult  to  realise  than  they 
appear  to  be,  especially  with  blowpipes  in  which  the  acetylene  is 
admitted  at  the  pressure  of  generation,  which  is  about  8  to  12  inches 
water  pressure.  A  great  difficulty  is  in  obtaining  the  requisite 
stability.  A  large  number  of  details  merit  attention,  such  as  ease 
of  manipulation  and  ease  of  taking  to  pieces  and  reassembling. 

52 


BLOWPIPES 


53 


The  velocity  of  propagation  is  about  330  feet  per  second  in  the  case 
of  oxygen  and  acetylene.  In  order  to  avoid  the  striking  back  of  the 
flame  it  is  necessary  that  the  velocity  of  the  mixture  at  the  exit 


should  be  of  the  same  value,  so  that  it  prevents  the  return  of  the 
flame  to  the  interior.  The  oxygen  being  under  pressure,  it  is  easy 
to  keep  this  gas  constant ;  but  acetylene  is  not  under  pressure,  and 
the  blowpipes  have  to  be  designed  to  get  the  amount  required  to 
complete  the  correct  mixture  for  combustion. 


54  MODERN  METHODS  OF  WELDING 

Low-pressure  blowpipes  are  designed  on  the  injector  principle, 
and  have  separate  internal  jets  for  the  oxygen  fixed  inside  the  blow- 
pipe. Such  a  jet  has  a  very  small  hole  bored  in  it,  the  size  being 
determined  by  the  size  of  the  blowpipe  for  whiqji  it  is  to  be  used. 


FIG.  19. — MULTIPLE  TIPS  UNIVERSAL  BLOWPIPE,  SMALL  SIZE. 

On  the  outside  of  this  inner  oxygen  jet  is  space  for  the  acetylene, 
which  is  attached  to  a  tube  (usually)  which  runs  along  the  pipe,  where 
the  rubber  tubing  is  fixed.  The  oxygen  under  pressure  rushes  out 
through  the  small  internal  jet,  in  the  place  where  the  acetylene  is; 


FIG.  20. — MULTIPLE  TIPS  UNIVERSAL  BLOWPIPE,  LARGE  SIZE. 

and  the  velocity  of  the  oxygen  draws  the  acetylene  with  it  to  the 
mixing  chamber  and  out  of  the  outer  nozzle,  in  the  proper  propor- 
tion required  for  a  good  steady  flame.  Most  injector  blowpipes 
are  designed  on  this  principle.  The  intimate  mixtures  of  the  gases 


BLOWPIPES      ,  55 

should  be  perfectly  accomplished  before  they  escape  from  the  blow- 
pipe. This  is  difficult  to  attain,  because  it  is  necessary  to  avoid  too 
much  loss  of  pressure,  which  would  demand  an  increase  in  the  pres- 
sure of  oxygen  in  order  to  regain  the  required  velocity  at  the  exit. 
This  would  be  detrimental  to  the  weld. 

A  blowpipe,  which  in  appearance  is  such  a  common  article, 
requires  such  precision  in  construction  that  it  can  only  be  under- 
taken by  specialists  in  the  subject.  It  is  essential,  indeed,  to  leave 
to  specialists  and  experts  not  only  the  design  and  construction  but 
even  the  repair  of  blowpipes.  Economy  and  good  results  in  weld- 
ing depend  largely  on  this.  Delivery  of  oxygen  being  fixed  by  the 
size  of  the  injector  orifice,  and  the  power  of  the  blowpipe  being 
invariable  in  these  limits,  therefore,  in  practice,  variation  of  pres- 
sure clearly  means  bad  welding.  The  makers  stamp  on  each  size 


FIG.  21. — ENDAZZLE  BLOWPIPE,  SINGLE  TIP  PATTERN. 

of  blowpipe  the  correct  pressure  at  which  it  will  work  and  give  the 
best  results.  This  pressure  should  not  be  increased.  It  is  quite  a 
common  practice  among  welders,  when  their  blowpipes  are  not 
working  well,  to  increase  the  oxygen  pressure  with  the  idea  of  getting 
a  better  flame.  This  is  a  very  bad  practice  indeed,  and  the  weld  is 
usually  spoilt.  Too  much  importance  cannot  be  laid  on  this  vital 
point.  Manufacturers  who  are  expert  in  their  line  would  not  stamp 
a  working  pressure  on  their  blowpipe  if  it  can  be  used  for  higher 
pressure. 

According  to  the  different  thicknesses  of  the  metal  to  be  welded, 
various  sizes  of  blowpipes  will  be  wanted.  The  pressures  and 
volumes  of  gases  required  varying  with  the  size  of  the  welds,  it  is 
necessary,  therefore,  to  have  blowpipes  designed  to  suit.  They 
range,  as  has  been  said,  from  1-5  to  100  cubic  feet  per  hour  of  acety- 
lene gas.  There  is  a  great  variety  of  blowpipes  at  present  on  the 
market — some  good,  some  medium,  and  some  bad.  All  operators 
should  make  themselves  fully  conversant  with  the  various  designs 
and  the  manufacture  of  the  same.  One  thing  that  must  be  remem- 
bered is  that  the  orifice  of  the  nozzle  of  any  blowpipe  is  proportionate 


56 


MODERN  METHODS  OF  WELDING 


to  the  delivery  of  the  injector  when  using  the  pressure  of  oxygen 
stipulated  by  the  makers.  It  is  essential  that  it  should  not  be 
reduced  or  enlarged.  If  it  were,  the  gases  would  not  be  correctly 
mixed  for  the  proper  combustion  for  a  stable  flame.  Almost 
the  first  blowpipes  for  low-pressure  welding  were  made  by 
Fouche,  a  Frenchman.  These  were  well  constructed  and  very 


FIG.  22. — ENDAZZLE  BLOWPIPE,  MULTIPLE. TIP  PATTERN. 

reliable  in  working.  In  fact,  they  are  still  more  reliable  than 
many  more  modern  ones.  Their  only  fault  was  that  they  were 
heavy.  Fig.  16  shows  one  in  section  and  one  in  elevation. 

The  "  Universal "  blowpipes  are  made  by  the  British  Oxygen  Com- 
pany. They  are  very  largely  used,  and  are  good  blowpipes.  They 
are  standardised,  and  new  parts  for  renewals  can  easily  be  got .  The 


BLOWPIPES 


57 


universal  blowpipes  may  have  either  a  fixed  or  interchangeable 
head.  The  two  kinds  are  practically  the  same  in  appearance  and 
construction.  In  the  interchangeable  set  there  are  loose  heads  of 
various  sizes,  with  one  handle  only.  The  heads  vary  in  power, 
and  are  numbered  to  correspond  with  the  proper  pressure  required. 


FIG.  23. — OSBORNE  BLOWPIPES,  FOUR  DIFFERENT  TYPES. 

The  small  siz3  is  supplied  with  seven  heads  ranging  from  2  to  8, 
and  the  larger  size  with  four  heads,  representing  8,  10,  12,  15. 
These  blowpipes  are  compact  and  useful. 

The  blowpipe  shown  on  p.  55,  known  as  the  "Endazzle,"  is  ex- 
tremely light,  and  has  a  unique  attachment:  a  pr 3  ssed-steel  hinged 
cover  over  the  rubber  tube  connectors.  These  open  right  out  to 
allow  the  rubber  tubes  to  be  fixed  on  the  ends  of  the  blowpipe,  and 


58  MODERN  METHODS  OF  WELDING 

then  afterwards  close  up,  which  prevents  the  hands  from  being 
burnt  should  ignition  take  place  at  the  handle  of  the  blowpipe. 
This  often  occurs  if  the  tubing  is  not  a  good  fit. 

The  type  below  (Figs.  24  and  25) — injector  heads  with  tips  com- 
plete— is  made  in  several  sizes  for  operating  on  different  sections  of 
metals.  For  greater  convenience  these  blowpipes  are  made  in  two 
models.  Each  model  is  supplied  complete  with  directions,  and  each 
injector  head  is  of  proper  proportions  to  produce  the  correct  mixtures 
of  gases  and  a  flame  of  perfect  stability  and  correct  dimensions 
according  to  the  work  for  which  it  is  intended.  Model  A  has  a 
range  of  injector  heads — sizes  0  to  4 — that  is,  five  different  blow- 
pipes (heads  only).  Model  B  has  a  range  of  injector  heads — 1  to 
9 — that  is,  nine  different  blowpipes  (heads  only).  This  covers  a  good 
range  and  will  weld  anything  from  TV  inch  to  1  inch  thick. 


SI 


FIG.  24. — SMALL  STYLE  C  WELDING  BLOWPIPE,  No.  453. 

These  blowpipes,  known  as  the  Davis-Bournonville  type  (Figs. 
24  and  25),  are  provided  in  two  standard  sizes — large  and  small — 
which  can  be  fitted  with  either  square  or  angle  heads  (45,  75, 
or  90  degrees),  and  straight  or  angle  hose  connections;  but  the 
standard  model  is  shown  here.  This  blowpipe  is  very  desir- 
able for  light  and  medium  sheet  metal  welding  and  light  repair 
work,  where  a  light,  compact,  nicely  balanced  tool  is  appre- 
ciated. Weight,  18  ounces;  length  over  all,  14  inches.  Fitted 
with  five  tips — Nos.  1,  2,  3,  4,  5,  style  99 — using  oxygen  pressures 
of  2,  4,  6,  8,  and  10  pounds  respectively.  It  is  used  to  advantage 
on  metal  ^V  to  T\  inch  thick. 

A  standard  blowpipe  for  heavy  welding,  and  for  general 
shop  work  requiring  a  strong  blowpipe.  Weight,  2  pounds; 
length  over  all,  20  inches.  Fitted  with  five  tips — Nos.  6,  7, 
8,  9,  10,  style  100 — using  oxygen  pressures  of  12,  14,  16,  18,  and 


BLOWPIPES  59 

20  pounds  respectively.     This  blowpipe  can  be   used   on  metal 
from  J-  inch  thick  upward. 

Consumption  of  Blowpipes. — Blowpipes  of  high,  medium,  and 
low  pressures  are  constructed  so  as  to  give  flames  of  all  intensities 
requisite  for  the  practice  of  autogenous  welding.  The  power  is 
reckoned  according  to  the  hourly  consumption  of  acetylene. 
Some  consume  1-7  to  100  cubic  feet  of  acetylene  per  hour,  or  20 
cubic  feet,  which  corresponds  to  the  hourly  delivery  of  acetylene 
The  blowpipe  with  the  lowest  consumption  uses  about  1  -5  cubic  feet 
per  hour  of  acetylene.  This  welds  sheet  iron  or  steel  up  to  TV  inch 
thick;  larger  blowpipes  consume  80  to  100  cubic  feet  of  acetylene 
per  hour,  and  these  weld  1-inch  thick  material. 

In  dealing  with  the  consumption  of  acetylene,  it  is  as  well  that 
we  should  deal  with  the  oxygen  at  the  same  time.     Theoretically 


f 


sic 


FIG.  25. — LARGE  STYLE  C  WELDING  BLOWPIPE,  No.  146. 

we  know  that  to  get  a  correct  mixture  and  a  neutral  flame  with  a 
small  white  cone  the  gases  must  be  mixed  in  equal  proportions — 
that  is,  1  volume  of  oxygen,  1  volume  of  acetylene,  when  measured 
under  normal  temperature.  Blowpipes  for  the  high  and  medium 
pressures  obtain  this  result  by  using  the  two  gases  under  equal 
pressures,  direct  from  the  two  cylinders — oxygen  and  acetylene. 
It  is  nearly  approached  in  blowpipes  in  the  medium-pressure 
system;  but  it  cannot  be  reached  in  the  low-pressure  system. 

It  is  general,  in  ordinary  works  practice,  to  use  1  of  acetylene 
to  1  -3  of  oxygen ;  it  is  only  in  well-designed  blowpipes,  working  under 
normal  conditions,  well-regulated  flame,  without  apparent  excess  of 
either  oxygen  or  acetylene,  and  an  expert  welder,  that  these  results 
are  obtained.  But  low-pressure  blowpipes  give  trouble  if  they  are 
not  well  taken  care  of  to  prevent  their  getting  knocked  about. 
Also  there  are  the  difficulties  with  the  regular  supply  of  acetylene 


60  MODERN  METHODS  OF  WELDING 

and  the  constant  pressure.  The  oxygen  being  under  pressure, 
it  is  difficult  to  mix  the  acetylene  in  absolutely  accurate  quantities 
in  order  to  give  it  sufficient  velocity. 

There  is  evidently  an  energetic  mixing  of  the  two  gases,  but  tht 
contact  is  not  molecule  to  molecule,  and  the  stream  lines  of  oxygen 
or  acetylene  can  escape  at  the  nozzle  without  being  mixed.  One  can 
test  this  in  different  ways — for  example,  by  contracting  the  exit 
tube  of  the  mixing  chamber,  or  by  increasing  the  pressure  of  the 
oxygen.  In  both  cases  the  proportion  of  oxygen  to  acetylene  is 
raised  considerably.  From  this  it  is  apparent  that  blowpipes  for 
low  pressure  use  least  oxygen  when  the  admission  pressure  of  oxygen 
is  least,  and  this  arrangement  for  obtaining  a  mixture  of  the  two 
gases  is  the  best.  In  some  blowpipes  the  oxygen  pressure  to  be  used 
corresponds  with  the  arrangement  of  the  mixing  chamber.  Change 
of  section  and  abrupt  bending  produce  a  loss  of  pressure.  One 
must  find  an  equilibrium  between  the  two  factors,  which  are  opposite. 
If  the  pressure  of  oxygen  is  not  raised  too  high,  the  arrangement  of 
mixing  is  excellent,  and  the  result  will  be  perfect.  From  prac- 
tice it  is  well  known  that,  as  the  welding  proceeds,  the  blowpipe 
becomes  heated,  and  the  gases,  especially  acetylene,  expand.  This 
causes  a  decrease  in  acetylene  gas,  and  makes  the  flame  at  once 
oxidising. 

From  tests  which  have  been  made  upon  the  consumption  of  the 
gases  by  the  Congress  on  Autogenous  Welding,  getting  fifty  blow- 
pipes from  the  different  manufacturers  (the  average  delivery  of 
acetylene  was  fixed  at  350  litres  per  hour,  and  the  work  to  be  executed 
lasted  from  thirty  to  forty  minutes:  the  welders  were  experts), 
the  best  proportion  of  oxygen  to  acetylene  was  1-12,  the  average 
1-3,  and  the  worst  1-9.  A  test  was  also  made  with  the  same  blow- 
pipe handled  by  two  welders,  one  using  oxygen  at  28  pounds  pressure 
and  the  other  at  13  pounds.  The  proportion  in  the  first  case  was 
1-83,  in  the  second  1-25,  showing  clearly  the  influence  of  excess 
pressure  of  oxygen  on  the  consumption  of  the  gas.  These  tests 
prove  that,  according  to  the  type  of  blowpipe  and  the  conditions  of 
use,  the  consumption  of  oxygen  for  a  constant  delivery  of  acetylene 
can  vary  greatly  and  may  double  in  volume.  Not  only  is  the  oxygen 
consumed  in  excess  of  the  theoretical  amount  a  pure  loss;  its  pres- 
ence in  the  flame  oxidises  the  metal,  lowers  the  strength  of  the  weld, 
and  renders  it  brittle  and  porous.  These  considerations  are  im- 
portant from  the  point  of  view  of  economy  and  good  work,  and  those 
interested  should  carefully  study  them. 

In  the  choosing  of  blowpipes  many  things. are  to  be  taken  into 


BLOWPIPES  61 

account;  if  it  is  to  be  used  for  continuous  work  on  one  thickness  of 
metal,  then  the  proper  sized  blowpipe  should  be  chosen  with  a  fixed 
delivery.  Then,  again,  one  must  satisfy  oneself  that  one  is  buying 
the  best  article,  not  so  much  as  regards  appearance  or  shape,  as 
with  a  view  to  lowest  consumption  for  the  particular  size  of  work ; 
and  a  guarantee  should  be  got  from  the  makers  for  a  stipulated 
hourly  consumption.  If  the  class  of  welding  is  changeable  from 
thick  to  lighter  materials,  then  a  combined  independent  set  with  all 
interchangeable  heads  would  be  most  suitable.  This  applies  to 
small  equipments  in  small  shops.  On  the  other  hand,  in  large  shops 
where  a  good  number  of  operators  are  employed  it  is  more  economi- 
cal to  have  fixed  ones ;  they  are  not  so  delicate  as  the  interchange- 
able, which,  by  the  constant  changing,  suffer  more  wear. 

The  actual  weight  is  often  important  in  practical  use.  Some- 
times welders  say  that  the  best  blowpipes  are  those  that  are  light 
in  the  hand ;  but  unless  they  have  attended  instructional  classes 
they  have  not  the  slightest  knowledge  of  the  consumption,  or  other 
details  which  must  be  settled  before  purchase.  If  the  work  is 
continuous,  then  a  light  blowpipe  should  be  adopted,  providing,  of 
course,  that  the  working  is  right,  with  the  correct  mixtures  of  gases 
and  the  consumption  up  to  standard.  If  the  work  is  heavy,  such 
as  some  repairs  which  have  to  be  done  quickly,  then  a  heavy  type 
would  be  preferable. 

The  questions  of  working,  the  consumption  of  the  gases,  and 
the  maintenance  in  the  workshop,  have  been  badly  neglected  in  the 
past.  As  competition  is  getting  keener  daily,  however,  manu- 
facturers are  now  interesting  themselves  in  the  details.  One  comes 
across  many  blowpipes  which  are  well  constructed  and  regulated, 
but  have  that  tiresome  striking  back  of  the  flame  into  the  interior 
when  the  nozzle  gets  heated.  This  is  a  serious  defect,  because  the 
welder  generally  increases  the  pressure  of  oxygen. 

A  guarantee  should  be  got  from  the  suppliers  that  this  back-firing 
will  not  take  place.  The  matter  of  consumption  is  a  vital  point  as 
regards  economy  and  cost.  In  large  shops,  where  there  are  one 
hundred  or  more  blowpipes  in  use  at  once,  the  saving  in  oxygen, 
with  the  very  best  designed  blowpipes,  giving  a  consumption  of 
T3  of  oxygen  to  1  of  acetylene,  may  amount  to  hundreds  of  pounds 
per  year. 

The  author  has  made  tests  in  this  direction,  one  of  which  may 
be  described  here.  Six  blowpipes  were  used,  two  each  of  different 
manufacture,  which  we  call  A  and  Al,  B  and  Bl,  C  and  Cl.  These 
tests  were  made  on  a  ^-inch  plate,  butt-welded,  with  12-gauge  thick 


62  MODERN  METHODS  OF  WELDING 

charcoal  iron  wire  as  the  welding-rod.     These  tests  lasted  twenty- 1 
five  minutes,  and  the  following  were  the  results: 

A  and  Al  gave  1-3  of  oxygen  to  1  of  acetylene. 
B    „    Bl     „     1-4 
C    „    Cl     „     1-75 

These  are  clear  instances  of  the  varying  makes  of  blowpipes, 
and  it  at  once  demonstrates  how  important  it  is  to  have  the  very 
best  designed  blowpipes  that  are  made.  As  a  further  illustration : 
suppose  a  bad  blowpipe,  using  1-75  of  oxygen  to  1  volume  of  acety- 
lene; say  that  the  consumption  of  the  works  is  4,000  cubic  feet 
per  month — that  is,  ten  cylinders  of  100  cubic  feet  each  per  week 
(many  firms  use  this  quantity  per  hour).  Under  these  conditions 
it  would  be — 

4000  *1-3  =2,971  cubic  feet. 
1*75 

The  loss  on  a  badly  designed  blowpipe  is,  therefore,  1,029  cubic 
feet,  which,  at  Id.  per  foot,  is  £4  5s.  9d.  per  month,  and  £51  9s.  per 
year.  This  is  only  10  cylinders  per  week — for  larger  users,  the  saving 
is  greater.  Apart  from  the  loss,  this  excess  of  oxygen  is  highly 
detrimental  to  the  welds,  which  is  much  more  serious  even  than  the 
loss  of  the  gas. 

Maintenance  of  Blowpipes. 

Users  of  blowpipes  must  bear  in  mind  always  that  they  are 
articles  of  precision.  They  are  made  on  delicate  lines,  to  be  deli- 
cately used,  and  not  to  hammer  the  weld  as  the  author  has  seen 
some  operators  do.  If  carefully  protected,  they  will  last  for  years, 
just  the  same  as  when  new.  The  taking  to  pieces  must  not  be  done 
with  cumbersome  tools,  and  in  cleaning  the  nozzles,  copper  wire 
should  be  used.  If  the  orifice  is  in  any  way  enlarged,  the  slightest 
alteration  in  section  produces  derangement,  f  The  blowpipe  section 
of  the  nozzle  corresponds  to  a  determined  flow  of  oxygen,  but  the 
orifice  for  the  flowing  of  the  oxygen  (the  injector)  remains  unchanged, 
and  any  increase  of  the  nozzle  opening  brings  about  a  decrease  of  the 
velocity  at  the  exit,  which  provokes  a  return  of  the  flame  into  the 
interior  of  the  blowpipe.  When  welding,  the  oxides,  or  particles  of 
metal,  produce  the  following  results : 

The  delivery  of  the  oxygen  being  variable  and  escaping  under 
greater  pressure  than  the  acetylene,  causes  the  flame  to  become 
oxidising  in  effect.  The  orifice  being  smaller  for  the  passages  of  the 


BLOWPIPES 


63 


two  gases,  it  is  the  stronger  (the  oxygen)  that  gets  through  in  pre- 
ference to  the  acetylene. 

One  must  never  allow  oil  or  grease  on  the  blowrpipes  or  tubes. 
as  in  oxygen  the  oil  may  catch  fire,  and  usually  burns  the  rubber 
tube.  This  often  happens  to  new  blowpipes,  in  which  the  oil  has 
got  inside  during  manufacture.)  Do  not  take  a  blowpipe  to  pieces 
unless  you  are  versed  in  its  component  parts,  especially  the  inner 


FIG.  26. — SHOWING  THE  CORRECT  NEUTRAL  FLAME,  MIDDLE  ONE  CORRECT. 


jet.  This  can  rarely  be  adjusted  again  in  the  same  place.  Before 
sending  out  they  are  adjusted  to  a  gauge,  and  one- thousandth  of 
an  inch  out  in  this  injector  sets  it  all  wrong.  The  best  and  quickest 
method  is  to  return  it  to  the  makers  for  repairs. 

If  a  blowpipe  is  obstructed  by  dust  or  other  particles  (generally 
lime  dust  carried  over  from  the  generator),  these  should  be  got  away 
by  fixing  the  rubber  tube  on  the  nozzle  end  of  the  blowpipea  leaving 


64 


MODERN  METHODS  OF  WELDING 


the  taps  open  and  turning  on  the  oxygen  temporarily.  This  should 
blow  it  quite  clean. 

All  operators  should  take  great  pride  in  blowpipes  trusted  to 
their  care,  and  should,  as  I  have  said  before,  treat  them  as  instru- 
ments of  precision,  keeping  them  ranged  in  good  order  and  always 
polished. 

The  following  are  a  few  hints  which  will  be  found  useful : 

(1)  See  that  the  blowpipe  is  in  good  order,  and  no  passages 
obstructed;  also  that  the  rubber  tubes  are  correct  and  securely 
fixed,  and  the  regulator  on  the  oxygen  cylinder  in  proper  working 
order. 

(2)  See  that  you  have  ample   acetylene   and   oxygen  for  the 
work  in  hand  before  commencing ;  it  is  injurious  to  the  weld  to  stop 
in  the  middle. 

(3)  Turn  the  oxygen  and  acetylene  taps  full  on,  and  light  the 
blowpipe.     The  flame  will  then  probably  have  an  excess  of  acetylene, 
which  should  be  reduced  by  gradually  turning  the  acetylene  tap 
on  the  blowpipe  (or  the  outlet  of  the  hydraulic  valve,  if  there  is  no 
tap  on  the  blowpipe),  until  the  flame  of  the  blowpipe  has  a  clearly 
defined  cone  at  the  orifice.      Fig.  26  shows  what  is  required.     The 
first  one  has  an  excess  of  acetylene;   the  second  is  correct;  and 
the  third  has  too  much  oxygen. 

(  Blowpipes  required  for  welding  by  the  oxy-acetylene  system 
must  be  chosen  with  care,  must  come  up  to  the  standard  rules,  and 
must  not  use  more  than  1-3  volumes  of  oxygen  to  1  of  acetylene. 
Also  they  must  be  easy  of  regulation,  easy  to  handle,  and  able  to  keep 
up  a  regular  and  stable  flame  over  long  periods  of  working) 

The  following  is  an  approximate  table,  giving  the  consumption 
of  each  size  of  blowpipe,  for  oxygen  and  acetylene;  the  size  of  the 
blowpipe  to  use,  with  the  thickness  of  the  plate  being  welded,  and 
the  length  of  feet  that  should  be  welded  per  hour.  These  tables 
are  very  useful  and  should  have  close  attention. 


Size  of  blowpipe 

2 

3 

4 

5 

6 

7 

8 

10 

12 

15 

Approximate   thickness   of    plate 

joint 

— 

— 

— 

I" 

— 

I" 

r 

\" 

i" 

1" 

Approximate  con-"| 

sumption      of[/   oxygen     . 

1-7 

3 

6-5 

9 

16 

23 

34 

48 

75 

100 

gases    per    hour  |  (acetylene    . 

1-2 

2 

4-3 

6-3 

11 

16 

24 

34 

48 

70 

in  cubic  feet    .  .  J 

Feet  welded  per  hour 

40 

30 

20 

15 

12 

9 

7 

4i 

2| 

1] 

CHAPTER  XII 
FLEXIBLE  TUBING 

No^welding  installation  is  complete  without  the  means  to  conduct 
the  gas  from  the  oxygen  cylinders  and  the  hydraulic  valves.  The 
gas  is  conveyed  by  rubber  tubing  fixed  on  the  proper  connectors, 
attached  to,  firstly,  the  blowpipe;  secondly,  the  hydraulic  safety 
valve;  and  thirdly,  the  regulator  on  the  oxygen  cylinder.  This 
rubber  tubing  is  very  important  in  any  installation,  and  unless  great 
care  is  taken  by  the  welders,  and  the  best  quality  of  rubber  purchased, 
it  is  an  expensive  maintenance  charge.  A  cheap  quality  of  rubber 
tubing  is  useless.  Some  of  that  on  the  market  contains  much  more 
loading  material  than  rubber.  Such  is  dear  at  any  price,  although 
in  appearance  there  is  not  much  to  choose.  The  best  tubing  con- 
sists of  a  good,  soft,  pliable  inside  rubber  liner,  of  good  stout  thickness 
and  not  less  than  f  inch  inside  clear  diameter,  reinforced  by  at 
least  three-ply  heavy  woven  canvas.  It  must  suit  the  connectors 
on  the  blowpipes,  regulators,  and  hydraulic  safety  valves.  The  fit 
should  be  just  sufficient  to  secure  a  gas-tight  joint  at  the  connectors, 
but  not  too  tight,  so  that  it  can  be  removed  without  undue  strain 
or  stretching  of  the  tubing.  There  are  60  lineal  feet  in  each  coil 
of  rubber  tubing,  and  these  usually  cut  into  four  pieces,  making  the 
requirements  for  two  operators  for  two  15  feet  each,  one  for  the 
acetylene  and  one  for  the  oxygen. 

This  rubber  tubing  is  badly  abused  in  the  workshop.  It  is  often 
blown  open  by  the  welders  suddenly  turning  the  oxygen  on  full  at 
high  pressure  when  the  blowpipe  tap  is  closed.  Also  at  times  they 
burn  the  tubing  whilst  welding,  unknown  to  themselves.  It  may  get 
accidentally  thrown  across  the  hot  article  which  is  being  welded, 
and  usually  this  is  not  found  out  till  a  hole  has  been  burnt  in  it. 
Again,  the  tubing  frequently  gets  cut  by  articles  dropped  on  to  it. 
On  making  an  examination  on  the  tubing  being  used,  it  will  often 
be  found  that  one  sample  in  five  is  leaking,  and  the  oxygen  blowing 
away  in  the  atmosphere.  This  is  a  costly  item  and  should  be 
watched  very  closely.  Often,  too,  the  tubing  ignites  at  the  connec- 
tor of  the  blowpipe,  because  the  rubber  liner  is  curled  up  inside 

65  5» 


66  MODERN  METHODS  OF  WELDING 

and  does  not  make  a  gas-tight  joint;  consequently,  the  oxygen 
escapes.  The  welder,  not  aware  of  this,  continues  welding  till  a 
spark  flashes  from  the  weld  and  ignites  the  rubber  tubing  at  the 
connector  of  the  blowpipe.  It  becomes  incandescent  immediately, 
probably  burning  the  operator's  hand,  unless  he  is  quick  enough 
to  drop  the  lighted  blowpipe.  It  is  necessary  to  have  tubing  of  the 
correct  size  to  fit  the  connectors,  so  as  to  avoid  the  bad  practice  of 
tying  with  wire. 

Neither  the  connector  nor  the  rubber  should  have  any  grease 
or  oil  on  it.  This  will  set  up  instant  combustion  if  any  oxygen 
catches  it.  If  the  end  of  the  tubing  is  hard  to  get  on,  it  should  be 
dipped  in  water.  This  will  ease  the  fixing  on  of  the  connectors. 
All  connections,  unfortunately,  are  not  alike,  which  makes  the  fitting 
of  tubing  awkward  where  the  connectors  vary.  It  would  be  a  great 
boon  if  all  manufacturers  of  these  connections  were  to  standardise 
the  sizes.  It  would  cheapen  production,  and  save  much  time  lost 
in  trying  to  get  one  size  tubing  on  another  size  connector.  For 
cutting  blowpipes,  the  rubber  tubing  must  be  very  much  stronger,  at 
least  five-ply,  owing  to  the  greater  pressure  required  for  cutting  iron 
and  steel. 

In  many  cases,  when  cutting  very  thick  plate  at  high  pressures, 
armoured  tubing  must  be  used. 

The  connectors  on  the  blowpipes,  regulators,  hydraulic  safety 
valves,  should  all  be  painted  with  shellac :  this  assists  in  keeping  the 
tubing  on  without  using  wire,  and  makes  a  tight  joint. 

The  present  system  of  connectors  for  the  rubber  tubing  is 
not  very  satisfactory,  and  new  ones  ought  to  be  brought  into  service. 
These  new  ones  consist  of  a  union  joint  with  coupling,  so  that  one 
half  of  the  union  can  be  fitted  on  the  gauge  on  the  cylinder,  and  the 
other  half  fitted  on  the  rubber  tubing  at  the  gauge  end.  These 
union  couplings  should  also  be  attached  to  the  hydraulic  safety  valve, 
and  at  the  other  end  of  the  tubing  to  that  which  is  attached  to  the 
gauge  on  the  cylinder,  and  the  same  union  couplings  on  the  blowpipe. 
The  great  advantage  is  that  half  the  coupling  is  fixed  permanently 
on  each  end  of  the  tubing,  thereby  saving  much  time  and  preserv- 
ing tubing. 


CHAPTER  XIII 
SAFETY    VALVES 

IT  is  a  well-known  fact  that  oxygen  and  acetylene  are  very  highly 
explosive,  and  it  is  indispensable  that  all  precautions  should  be 
taken  to  prevent  the  formation  of  these  combustible  gases.  Their 
use  is  becoming  more  and  more  general  in  every  part  of  the  country, 
and  we  have  therefore  to  put  forward  continually  that  precautions 
must  be  taken  to  prevent  their  formation,  especially  as  their  inflam- 
mation is  very  easily  produced.  With  acetylene  in  use  at  a  lower 
pressure  than  oxygen,  the  oxygen  can  return  in  the  acetylene  tubes 
and  piping  and  so  combine  this  gas  in  the  generator.  This  occurs 
when  there  is  a  partial  obstruction  of  the  blowpipe,  caused  often  by 
the  welder  allowing  the  blowpipe  suddenly  to  touch  the  molten  metal. 
The  oxygen,  being  under  pressure,  and  as  the  outlet  is  blocked, 
flows  up  the  acetylene  tube  into  the  safety  valve  or  hydraulic  seal. 

Therefore  it  is  absolutely  essential  to  place  in  the  acetylene 
piping,  between  the  generator  and  the  rubber  acetylene  tubes  on  the 
blowpipes,  an  arrangement  capable  of  arresting  immediately  any 
return  of  the  oxygen.  The  object  of  a  safety  valve  is  to  direct  into 
the  open  air  any  oxygen  which  returns  in  the  direction  of  the  acety- 
lene. It  is  not  really  meant  to  stop  back-fire,  but  to  prevent  forma- 
tion of  a  mixture  of  high  explosive  gases  by  the  return  of  the  flame. 

The  efficacy  of  such  an  apparatus  must  be  absolute.  So  far  a 
simply  designed  water  seal  has  proved  the  most  effective.  It  is  one 
that  cannot  go  wrong  if  the  water  level  is  kept  right.  In  the  hydrau- 
lic safety  valve,  two  tubes  emerge  from  a  layer  of  water,  one  for  the 
entry  of  the  gas  and  the  other  open  to  the  exterior,  placed  at  different 
levels,  constituting  an  absolute  barrier  against  all  return  of  the 
oxygen  in  the  acetylene  piping.  Other  arrangements,  not  based 
on  this  principle,  should  be  rejected. 

The  illustration  (Fig.  27)  shows  a  good  standard  type  made  by 
the  British  Oxygen  Company.  The  acetylene  pipe  from  the  gas- 
holder or  main  supply  is  connected  with  tap  A,  and  the  acetylene 
tube  leading  to  the  blowpipe  is  connected  with  tap  B.  C  is  a  loosely 
fitting  lid,  covering  the  cup  in  which  the  water  is  poured  to  charge 

67 


68 


MODERN  METHODS  OF  WELDING 


the  seal  pot  D  up  to  the  level  of  the  tap  E.  Taps  A  and  B  must  be 
closed  whilst  the  seal  pot  D  is  being  charged  with  water.  When 
water  shows  at  tap  E,  immediately  stop  filling,  and,  allowing  time 
for  the  surplus  water  to  drain  off,  close  the  tap  E.  The  lid  C  must 


FIG.  27.— SAFETY  VALVE,  ELEVATION  AND  SECTIONAL. 

then  be  replaced,  and  the  taps  A  and  B  may  be  opened.     The  valve 
is  then  in  working  order. 

The  filling  pipe  F  is  made  long  enough  to  hold  a  column  of  water 
greater  than  the  pressure  of  the  acetylene  generator.  There  should 
not  be  less  than  8  inches  of  water.  When  at  work  the  taps  A  and  B 
must  be  open,  and  the  supply  of  acetylene  regulated  by  the  tap  on 
the  blowpipe.  Should  the  blowpipe  nozzle  at  any  time  become 


SAFETY  VALVES 


69 


choked  whilst  the  oxygen  supply  remains  unchecked,  the  gas  would 
be  forced  by  its  superior  pressure  along  the  acetylene  tube.  The 
back  pressure  thus  caused,  acting  on  the  surface  of  the  water  in  the 
seal  pot  D,  would  seal  the  acetylene  pipe  and  force  the  water  up  the 
pipe  F,  displacing  the  liquid  C.  The  hydraulic  seal  to  the  atmo- 


Centrejm     oF  Cock 
|U  'Brass 


tsi 


FIG.  28. — STANDARD  SECTIONAL  TYPE  SAFETY  VALVE. 

sphere  would  thus  be  destroyed  and  both  gases  would  escape  until 
taps  A  and  B  were  closed.  Thus  oxygen  can  never  penetrate  the 
acetylene  supply  beyond  the  hydraulic  valve,  provided  the  valve 
is  kept  properly  filled. 

There  is  really  very  little  scope  for  modification  in  the  design 
of  these  hydraulic  valves.     Two  conditions,  however,  are  essential 


70  MODERN  METHODS  OF  WELDING 

— viz.,  that  the  pipe  conveying  acetylene  from  the  generator  dis- 
charges into  the  water  seal  pot  at  a  lower  level  than  the  opening  to 
the  vent ;  and  that  the  vent  pipe  has  a  direct  vertical  discharge  from 
the  seal  pot  into  the  atmosphere. 

All  hydraulic  back-pressure  valves  must  be  fixed  on  the  acetylene 
supply  pipe  in  a  vertical  position,  as  near  to  the  blowpipe  as  con- 
venience will  permit.  A  good  position  is  on  a  wall,  with  the  bottom 
of  the  valve  about  4  feet  from  the  ground.  The  acetylene  inlet  pipe, 
coupled  to  the  tap  A,  should  extend  vertically  several  feet  above  the 
tap.  In  cases  where  two  or  more  blowpipes  are  worked  from  the 
same  acetylene  supply  a  separate  hydraulic  back-pressure  valve 
should  be  employed  for  each. 

One  must  be  very  careful  in  the  choice  of  hydraulic  back-pressure 
valves.  A  serious  explosion,  resulting  in  grave  injuries  to  more  than 
one  workman  and  the  total  destruction  of  an  acetylene  generator, 
occurred  in  a  munition  works  in  Yorkshire  in  May,  1917.  The  holder 
formed  part  of  a  large  plant  which  had  been  in  successful  operation 
for  several  years.  Suspicion  not  unnaturally  attached  itself  to  the 
hydraulic  valve. 

No  part  of  an  oxy-acetylene  outfit  is  more  important  or  requires 
more  careful  attention  than  the  hydraulic  back-pressure  valve. 
The  explosion  in  question  was  caused  by  a  badly  designed  hydraulic 
back-pressure  valve  of  German  make,  in  which  there  was  a  U-tube 
fitted,  one  end  of  which  was  fixed  in  the  seal  pot,  and  the  difference 
between  the  U-pipe  and  the  supply  pipe  was  not  sufficient  to  make  a 
satisfactory  seal.  It  is  obvious  that  such  a  valve  as  this  is  useless 
as  the  means  of  preventing  oxygen,  at  its  superior  pressure,  from 
flowing  back  to  the  acetylene  generator.  The  essential  method  of 
working  is  for  the  acetylene  to  bubble  through  a  small  height  of 
water,  which  is  nevertheless  sufficient  for  covering  the  tube  leading 
to  the  exterior,  this  being  between  the  surface  of  the  water  and  the 
level  of  the  escaping  acetylene.  The  valves  must  not  be  too  large 
a  gas  capacity.  The  diameter  of  the  body  should  just  be  suffi- 
cient to  retain  the  level  of  the  water  constant,  and  the  height  enough 
to  avoid  drops  of  water  reaching  the  outlet  of  the  acetylene.  The 
pipe  which  comes  from  the  main  supply  into  the  seal  pot  should  be  of 
suitable  diameter  for  maximum  delivery  to  the  largest  blowpipe, 
so  as  to  avoid  all  loss  of  pressure. 

Often  a  pipe  of  small  diameter,  when  a  large  blowpipe  is  used, 
causes  eddies  in  the  flow  of  the  gas,  through  the  delivery  not  being 
sufficient.  The  pipe  which  leads  from  the  generator  should  go 
through  the  seal  pot  to  within  J  inch  of  the  bottom.  The  bottom 


SAFETY  VALVES  71 

end  of  this  should  be  shaped  in  the  form  of  a  cone,  and  the  cone  should 
have  small  holes  drilled  in  it  to  allow  the  gas  to  spread  more  when 
passing  through  the  water.  The  height  of  the  water  in  the  seal  pot 
should  be  about  3  inches  clear  of  the  top  holes  in  the  cone.  This 
will  be  the  position  of  the  test  tap.  The  acetylene  outlet  tap  will 
be  about  8  inches  above  this.  The  atmosphere  pipe  should  be  placed 
half-way  between  the  test  tap  and  the  holes  of  the  inlet  acetylene  pipe. 
The  height  of  this  pipe  depends  on  the  pressure  of  the  acetylene, 
since  the  water  rises  in  this  tube  as  the  pressure  of  the  gas  is  in- 
creased. The  height  should  be  related  to  the  level  of  the  water  in 
the  valve,  and  should  be  more  than  the  greatest  possible  pressure 
that  would  be  used  in  the  generators. 

The  illustration  (Fig.  28)  shows  a  valve  that  is  infallible  in  working 
and  is  simple  in  construction.  It  can  easily  be  made  by  any  in- 
telligent man.  It  consists  of  one  piece  of  solid  drawn  tube,  3  inches 
inside  diameter,  with  discs  welded  top  and  bottom.  The  bottom 
disc  should  have  a  quarter  gas  socket  welded  on,  to  take  a  tap  to 
drain  the  water  out  when  this  is  required  for  cleaning  purposes. 
Gas  sockets  may  also  be  welded  at  each  of  the  tap  holes  for  screwing 
them  in.  The  acetylene  inlet  tube  and  the  filling  tube  may  both  be 
welded  in  the  disc  top  before  welding  the  top  on ;  but  one  must  be 
careful  to  get  the  tubes  fixed  at  the  proper  depth  before  welding 
them  in. 

The  outside  tube  terminates  in  a  funnel,  which  is  used  for  filling 
the  valve  with  water.  This  is  covered  by  a  lid.  Well-designed  and 
well-constructed  hydraulic  valves  work  well,  are  safe,  and  do  not 
get  out  of  order.  It  is  only  necessary  to  verify  the  level  of  the  water 
daily,  or  every  time  it  is  left  standing,  and  all  operators  should  see, 
and  make  a  practice  of,  trying  the  test  tap  not  less  than  twice  a  day. 


CHAPTER  XIV 

PURIFIERS 

PURIFIERS  generally  consist  of  cylindrical  vessels,  usually  made  of 
sheet  steel  with  an  airtight  lid  or  cover.  They  usually  contain  a 
series  of  trays  holding  the  purifying  materials.  The  calcium  carbide, 
as  now  manufactured,  is  by  no  means  a  chemically  pure  substance. 
It  includes  a  large  number  of  foreign  bodies.  In  crude  acetylene, 
these  are  partly  gaseous,  partly  liquid,  partly  solid.  They  may 
render  the  gas  dangerous  from  the  point  of  view  of  possible  explo- 
sions. They,  or  the  products  derived  from  them  on  combustion, 
may  be  harmful  to  the  health  if  inhaled.  They  are  objectionable 
at  the  burner  orifices,  by  determining,  or  assisting  in,  the  defects  of 
the  metals  of  the  weld. 

A  proper  system  of  purification  is  one  that  is  competent  to 
remove  the  carbide  impurities  from  the  acetylene,  as  far  as  that 
removal  is  desirable  or  necessary.  The  generator  impurities,  as 
stated  above,  are  oxygen,  nitrogen,  and  lime  in  the  form  of  fine  dust. 
This  lime  may  be  extracted  when  the  gas  is  passing  from  the  genera- 
ting chambers  along  the  outlet  pipe  and  down  again  through  the  bent 
pipe  which  dips  in  the  water  of  the  tank.  As  the  gas  bubbles  through 
the  water,  part  of  the  lime  dust  is  removed.  What  escapes  extrac- 
tion may  be  removed  by  passing  the  gas  through  cotton-wool  or  felt, 
which  is  usually  placed  over  the  purifying  material,  in  the  top  of  the 
purifier. 

The  least  volatile  liquid  impurities  will  be  removed  partly  in  the 
condenser  (if  one  is  fixed),  partly  in  the  washer  (the  tank),  and 
partly  by  mechanical  dry-scrubbing  action  of  the  solid  purifying 
material  in  the  chemical  purifier.  Sufficient  removal  of  these  genera- 
tor impurities  need  throw  no  appreciable  extra  labour  upon  the  con- 
sumer of  acetylene,  for  one  can  readily  select  a  type  of  generator 
in  which  the  production  is  reduced  to  a  minimum,  using  a  cotton- 
wool or  coke  filter  for  the  gas.  A  water  washer,  which  is  very  useful 
in  the  plant,  if  only  employed  as  a  non-return  valve  between  the 
generator  and  the  main  piping  and  the  indispensable  chemical  puri- 

72 


PURIFIERS  73 

fiers,  will  take  out  of  the  acetylene  all  the  remaining  generator  im- 
purities which  need  to,  and  can,  be  extracted. 

In  designing  a  washer  for  the  extraction  of  the  ammonia  and 
sulphuretted  hydrogen,  it  is  necessary  to  see  that  the  gas  is  brought 
into  most  intimate  contact  with  the  liquid,  while  no  more  pressure 
than  can  be  avoided  is  lost.  One  volume  of  water  only  absorbs 
about  3  volumes  of  sulphuretted  hydrogen  at  atmospheric  tempera- 
ture, but  takes  up  some  600  volumes  of  ammonia ;  and,  as  ammonia 
always  accompanies  the  sulphuretted  hydrogen,  the  latter  may  be 
said  to  be  absorbed  in  the  washer  by  a  solution  of  ammonia,  a  liquid 
in  which  sulphuretted  hydrogen  is  much  more  soluble.  Since  the 
water  only  dissolves  about  an  equal  volume  of  acetylene,  the  liquid 
in  the  washer  will  continue  to  extract  ammonia  and  sulphuretted 
.hydrogen  long  after  it  is  saturated  with  the  hydrocarbon.  To  avoid 
waste  of  acetylene  by  dissolution  in  the  clean  water  of  the  washer, 
the  plan  is  sometimes  adopted  of  introducing  water  into  the  genera- 
tor through  the  washer  so  that,  practically,  the  carbide  is  always 
attacked  by  a  liquid  saturated  with  acetylene.  For  compactness 
and  simplicity  of  parts,  the  water  of  the  holder  seal  is  often  used  as 
a  washing  liquid.  But  unless  the  liquid  of  the  seal  is  constantly 
renewed  it  will  become  offensive,  and  will  act  corrosively  on  the 
metal  of  the  tank  and  bell. 

The  reason  why  the  carbide  impurities  must  be  removed  from 
acetylene  is  this:  There  are  three  compounds  of  phosphorus,  all 
termed  phosphuretted  hydrogen  or  phosphine— a  gas  PH2,  a  liquid 
P2H4,  and  a  solid  P4H2.  The  liquid  is  spontaneously  inflammable 
in  the  presence  of  air — that  is  to  say,  it  catches  fire  of  itself,  without 
the  assistance  of  a  spark  or  flame,  immediately  it  comes  in  contact 
with  the  atmospheric  oxygen.  Being  very  volatile,  it  is  easily 
carried  away  as  vapour  by  any  permanent  gas.  In  commercial 
carbide  it  has  been  found  that  the  highest  amount  of  phosphine  in 
the  acetylene  is  2-3  per  cent.,  and  this  gas  is  capable  of  self -inflamma- 
tion. Bullier  states  that  acetylene  must  contain  80  per  cent,  of 
phosphine  to  render  it  spontaneously  inflammable. 

Ammonia  is  objectionable  in  acetylene  because  it  corrodes  the 
brass  fittings  and  pipes,  and  because  it  is  partly  converted  into 
nitrous  and  nitric  acids  as  it  passes  through  the  flame. 

Sulphur  is  objectionable  in  acetylene  because  it  is  converted 
into  sulphurous  and  sulphuric  anhyhrides,  and  their  respective  acids, 
as  it  passes  through  the  flame. 

Phosphorus  is  objectionable  because,  in  similar  circumstances, 
it  produces  phosphoric  anhydride  and  phosphoric  acid.  Each  of 


74 


MODERN  METHODS  OF  WELDING 


these  acids  is  harmful  to  the  human  system,  sulphuric  and  phos- 
phoric anhydrides  (S02  and  P4O10)  acting  as  a  specific  irritant  to 
the  lungs  of  persons  predisposed  to  affections  of  the  bronchial 
organs. 

Phosphorus,  however,  has  a  further  harmful  action.  Sulphuric 
anhydride  is  an  invisible  gas,  but  phosphorous  anhydride  is  a  solid 
body,  and  is  produced  as  an  extremely  fine,  light,  white,  voluminous 
dust,  which  causes  a  more  or  less  opaque  haze.  Phosphoric  anhy- 
dride is  also  partly  deposited  in  the  solid  state  at  the  burner  orifice, 


FIG.  29. — PURIFIER,  SHOWING  SECTION  AND  ELEVATION  WITH  PURIFYING  MATERIAL. 

and,  always  assisting  in  the  deposition  of  carbon  from  any  poly- 
merised hydrocarbon  in  the  acetylene,  thus  helps  to  block  up 
and  distort  the  orifices  of  the  blowpipes. 

Purifiers  are  usually  made  from  sheet  iron  or  steel  and  galvanised, 
and  often  in  good  plants  contain  a  porcelain  vessel  for  holding  the 
purifying  materials,  as  acid  from  some  of  these  act  on  the  mild 
steel  shell,  corroding  it.  Fig.  29  shows  a  purifier  made  from  sheet 
steel,  in  which  all  the  joints  are  welded,  and  the  connecting  pipes 
also  welded  in ;  the  purifying  material  is  put  into  trays,  the  bottom 
of  which  is  perforated  with  small  holes.  The  lowermost  tray  is  set 
about  3  inches  from  the  bottom,  the  other  trays  on  the  top  of  this, 


PURIFIERS 


75 


leaving  a  space  of  about  J  inch  between  each  tray.  In  the  bottom 
of  each  tray  is  a  layer  of  thin  felt,  to  prevent  the  purifying  material 
from  passing  through  the  holes  and,  secondly,  to  act  as  drier  for 
the  gas.  On  the  top  of  all  the  trays  is  a  layer  of  felt  or  cotton-wool, 
put  in  to  extract  the  lime  dust  which  has  not  been  extracted  by 
the  water  filter,  and  which  came  over  with  the  gases.  This  dust- 
is  thereby  prevented  from  getting  into  the  blowpipe  or  the  weld. 

The  purifying  material  should  be  lightly  placed  in  the  trays 
so  as  to  allow  the  gases  to  go  freely  through  the  material  without 
choking.  It  is  usual  for  the  inlet  pipe  to  be  at  the  bottom,  and  the 


FIG.  30.  —  ATOX  PURIFIER. 


outlet  pipe  at  the  top,  and  a  water  tap  must  be  placed  at  the  bottom 
to  allow  the  water  from  condensation  to  be  run  off  from  time  to 
time.  It  is  important  that  this  be  tried  frequently,  as  the  water 
may  be  sufficient  to  rise  up,  and  through  the  purifying  material, 
thereby  nullifying  its  properties.  The  purifier  may  be  placed  any- 
where between  the  generator  and  the  main  piping,  but  it  is  usually 
near  the  generator. 

In  the  systematic  purification  of  acetylene  the  practical  question 
arises,  How  is  the  attendant  to  tell  when  the  purifiers  approach 


76  MODERN  METHODS  OF  WELDING 

exhaustion  and  need  recharging?  Heil  has  stated  that  the  purity  of 
the  gas  may  be  judged  by  its  atmospheric  flame  given  by  a  Bunsen 
burner.  Pure  acetylene  gives  a  perfectly  transparent,  moderately! 
dark  blue  flame,  which  has  an  inner  cone  of  pale  yellowish-green  I 
colour,  whilst  the  impure  gas  yields  a  longer  flame  of  an  opaque 
orange-red  tint  with  a  bluish-red  inner  cone.  It  must  be  noted, 
however,  that  particles  of  lime  dust  in  the  gas  may  cause  the  atmo- 
spheric flame  to  be  reddish  or  yellowish  (through  the  action  of  calcium 
or  sodium),  quite  apart  from  the  ordinary  impurities. 

The  simple  method  of  ascertaining,  definitely,  whether  a  purifier 
is  sufficiently  active  consists  in  the  use  of  test  papers  prepared  to  the 
prescription  of  G.  Keppler.  These  papers  are  cut  to  a  convenient 
size,  are  put  up  in  book  form,  and  may  be  torn  one  at  a  time.  In 
order  to  test  whether  the  gas  is  sufficiently  purified,  one  of  the  papers 
is  moistened  with  hydrochloric  acid  of  10  per  cent,  strength,  and  the 
gas  issuing  from  the  blowpipe,  or  pet  cock,  is  allowed  to  impinge 
on  the  moistened  part.  The  original  black  or  grey  colour  of  paper 
is  changed  to  white  if  the  gas  contains  a  notable  amount  of  impurity, 
but  remains  unchanged  if  the  gas  is  adequately  purified. 

The  Keppler  test  papers  turn  white  when  the  gas  contains  either 
ammonia  phosphine,  siliciuretted  hydrogen,  sulphuretted  hydrogen, 
or  organic  sulphur  compounds,  but  for  carbon  disulphide  that 
change  is  slow.  Thus  the  paper  serves  as  a  test  for  all  impurities 
likely  to  occur  in  acetylene.  The  paper  is  a  specially  prepared  black 
porous  kind  which  has  been  dipped  in  a  solution  of  mercuric  chloride 
(corrosive  sublimate)  and  dried.  These  papers  can  be  obtained, 
put  up  in  case  with  a  bottle  of  acid  for  moistening  them  as  required, 
from  E.  Merck,  16  Jewry  Street,  London,  E.G.  3,  or  from  the  usual 
retail  dealers  in  chemicals. 

The  sensitiveness  of  the  test  is  quick.  If  a  distinct  white  mark 
appears  on  the  moistened  paper  when  it  is  exposed  for  five  minutes 
to  a  jet  of  acetylene,  the  latter  is  inadequately  purified.  If  the  gas 
has  passed  through  a  purifier  this  test  indicates  that  the  material 
is  not  efficient,  that  the  purifier  needs  recharging. 

The  British  Acetylene  Association  has  issued  the  following  set  of 
regulations  as  to  purifying  materials  and  purifiers  for  acetylene : 

(1)  The  purifying  material  shall  remove  phosphorus  and  sulphur 
compounds  to  a  commercial  degree — e.g.,  not  to  a  greater  degree 
than  will  allow  easy  detection  of  escaping  through  its  odour. 

(2)  The  purifying  material  shall  not  yield  any  products  capable 
of  corroding  the  gas  mains  or  fittings. 

(3)  The  purifying  material  shall,  if  possible,  be  efficient  as  a 


PURIFIERS  77 

drying  agent,  but  the  Association  does  not  consider  this  absolutely 
necessary. 

(4)  The  purifying  material  shall  not,  under  working  conditions, 
be  capable  of  forming  explosive  compounds  or  mixture.     It  is  under- 
stood, naturally,  that  this  condition  does  not  apply  to  the  un- 
avoidable mixture  of  the  acetylene  and  air  formed  when  charging 
the  purifier. 

(5)  The   apparatus  containing  the  purifying  material  shall  be 
a  simple  construction  and  capable  of  being  recharged  by  an  in- 
experienced person  without  trouble.     It  should  be  so  designed  as  to 
bring  the  gas  into  proper  contact  with  the  material. 

(6)  The  containers  and  purifiers  should  be  made  of  such  materials 
as  are  dangerously  affected  by  the  respective  materials  used. 

(7)  No  purifier  should  be  sold  without  a  card  of  instructions 
suitable  for  hanging  up  in  some  prominent  place.     Such  instructions 
should  be  of  the  most  detailed  nature,  and  should  not  presuppose 
any  expert  knowledge  whatever  on  the  part  of  the  operator. 


CHAPTER  XV 
SELECTION  AND  INSTALLATION 

IT  is  not  possible  to  give  a  direct  answer  to  the  question  as  to  which 
is  the  best  type  of  acetylene  generator.  There  are  no  generators 
made  by  responsible  firms  which  are  not  safe.  Some  are  easier  to 
charge  and  clean  than  others.  Some  require  more  frequent  atten- 
tion. Some  have  moving  parts  less  likely  to  fail,  or  none  at  all  to 
go  wrong.  There  are  contact  apparatus  on  the  market  which  appear 
to  give  little  trouble.  There  is  very  little  to  choose,  from  the  chemi- 
cal and  physical  view,  between  the  generators  now  on  the  market. 
A  selection  may  rather  be  made  on  mechanical  grounds. 

The  generator  must  be  well  able  to  produce  gas  as  rapidly  as 
ever  it  will  be  required  during  the  longest  time  the  blowpipe  may 
be  used.  It  must  be  strong  and  able  to  bear  careless  handling  and 
frequent  rough  manipulation  of  its  parts.  It  must  be  built  of  sound 
material,  and  galvanised  after  manufacture,  so  that  it  will  not  rust 
in  a  few  years.  Each  and  every  part  must  be  accessible,  and  its 
exterior  visible.  Its  pipes  for  the  gas  must  be  large  bore.  The 
number  of  cocks,  valves,  and  moving  parts  must  be  reduced  to  a 
minimum.  It  must  be  easy  to  clean,  the  waste  lime  must  be  readily 
removed.  It  must  be  so  fitted  with  vent  pipes  that  the  pressure 
can  never  rise  above  that  at  which  it  is  supposed  to  work.  Appara- 
tus that  claims  to  be  automatic  should  be  perfectly  automatic, 
the  water  or  the  carbide  feed  being  locked  automatically  before  the 
carbide  store,  the  decomposing  chamber,  or  the  sludge  cock  can  be 
opened. 

The  generating  chamber  must  always  be  in  communication  with 
the  atmosphere  through  a  water  seal  vent  pipe,  the  seal  of  which, 
if  necessary,  the  gas  can  blow  at  any  time.  All  apparatus  should  be 
fitted  with  rising  holders,  and  the  larger  the  better.  The  best  place 
for  a  generator  is  in  the  open  air,  or  a  simple  open  shed,  if  well  venti- 
lated. The  diameter  of  the  mains  and  service-pipes  for  an  acetylene 
installation  must  be  such  that  the  main  or  pipe  will  convey  the 
maximum  quantity  of  gas  likely  to  be  required  to  feed  properly  all 
the  blowpipes  which  are  connected  to  it,  without  an  excessive  actua- 

78 


SELECTION  AND  INSTALLATION  79 

ting  pressure  being  called  upon  to  drive  the  gas  through  the  main 
or  pipe. 

The  practical  question  in  gas  distribution  is,  What  quantity  of 
gas  will  a  given  actuating  pressure  cause  to  flow  along  a  pipe  of  given 
length  and  given  diameter  ?  The  solution  of  this  question  allows 
of  the  diameter  of  the  pipes  being  arranged  so  far  that  they  carry 
a  required  quantity  of  gas  a  given  distance  under  the  actuating 
pressure  that  is  most  convenient  or  appropriate.  In  order  to  avoid, 
as  far  as  possible,  expenditure  and  labour  in  repeating  calculations, 
tables  have  been  drawn  up  from  Morel's  formulae,  which  will 
serve  to  give  the  requisite  information  as  to  the  proper  sizes  of  pipes 
to  be  used  in  the  cases  likely  to  be  met  with  in  ordinary  practice. 

Piping  used  for  the  distribution  of  acetylene  must  be  sound  in 
itself,  and  the  joints  perfectly  tight.  Ordinary  gas  barrel  is  not  good 
enough.  Joints  for  acetylene,  like  those  for  steam  or  high-pressure 
water,  must  be  made  tight  by  using  well-threaded  fittings,  so  as  to 
secure  metallic  contact  between  pipe  and  socket.  Acetylene  service 
should,  wherever  possible,  be  laid  with  a  fall,  which  may  be  very 
slight,  towards  a  small  closed  vessel  adjoining  the  gas-holder  or 
purifier,  in  order  that  water  deposited  from  the  gas  through  condensa- 
tion of  aqueous  vapour  may  run  out  of  the  pipe  into  that  apparatus. 
Where  it  is  impossible  to  secure  an  interrupted  fall  in  that  direction, 
there  should  be  inserted  in  the  service  pipe  at  the  lowest  point  of  each 
dip  it  makes,  a  short  length  of  pipe  turned  downwards  and  termina- 
ting in  a  plug  or  sound  tap,  to  remove  the  condensed  water. 

When  all  the  fittings  have  been  connected,  the  whole  system  of 
pipes  must  be  tested  by  putting  it  under  a  gas  (or  air)  pressure  of 
9  to  12  inches  of  water,  and  observing  on  an  attached  pressure-gauge 
whether  any  fall  in  pressure  occurs  within  fifteen  minutes  after  the 
main  inlet  tap  has  been  shut.  The  pressure  required  for  this  can  be 
obtained  by  weighing  the  holder.  If  the  gauge  shows  a  fall  of  pres- 
sure of  J  inch  or  more  in  these  circumstances,  the  pipes  must  be 
examined  until  the  leak  is  located,  but  it  must  never  be  searched 
for  with  a  light.  Fittings  for  acetylene  must  have  perfectly  sound 
joints  and  taps — common  gas  fittings  will  not  do;  the  joints,  taps, 
ball  sockets,  etc.,  are  not  ground  accurately  enough  to  prevent 
leakage.  Fittings  are  now  being  specially  made  for  acetylene, 
which  is  a  step  in  the  right  direction. 

The  conditions  which  a  generator  should  fulfil  before  it  can 
be  considered  safe  are  as  follows : 

(1)  The  temperature  in  any  part  of  the  generator  when  run  at 
the  maximum  rate  for  which  it  is  designed,  for  a  prolonged  period, 


80  MODERN  METHODS  OF  WELDING 

should  not  exceed  130°  C.  This  may  be  ascertained  by  placing  short 
lengths  of  wire,  drawn  from  fusible  metal,  in  those  parts  of  the 
apparatus  in  which  heat  is  likely  to  be  generated. 

(2)  The  generator  should  have  an  efficiency  of  not  less  than  90 
per  cent.,  which,  with  carbide  yielding  5  cubic  feet  per  pound,  would 
imply  a  yield  of  4-5  cubic  feet  of  gas  for  each  pound  of  carbide  used. 

(3)  The  size  of  the  pipes  carrying  the  gas  should  be  proportional 
to  the  maximum  rate  of  generation,  so  that  undue  back-pressure 
from  throttling  may  not  occur. 

(4)  The  carbide  should  be  completely  decomposed  in  the  appara- 
tus, so  that  the  lime  sludge  discharged  from  the  generator  shall  be 
incapable  of  generating  more  gas. 

(5)  The  pressure  at  any  part  of  the  apparatus,  on  the  side  of  the 
holder,  should  not  exceed  that  of  250  inches  of  water,  and  on  the 
service  side  of  same,  or  where  no  gas-holder  is  provided,  should  not 
exceed  200  inches  of  water. 

(6)  The  apparatus  should  give  no  tarry  or  other  heavy  condensa- 
tion products  from  the  decomposition  of  the  carbide. 

(7)  In  the  use  of  a  generator,  regard  should  be  had  to  the  danger 
of  a  stoppage  of  the  passage  of  the  gas,  and  the  resulting  increase 
of  pressure  which  may  arise  from  the  freezing  of  water.     Where 
freezing  may  be  anticipated,  steps  should  be  taken  to  prevent  it. 

(8)  The  apparatus  should  be  so  constructed  that  no  lime  sludge 
can  gain  access  to  any  pipes  intended  for  the  passage  or  circulation 
of  water. 

(9)  The  air  space  in  a  generator  before  charging  should  be  as 
small  as  possible. 

(10)  The  use  of  copper  should  be  avoided  in  such  parts  of  the 
apparatus  as  are  liable  to  come  in  contact  with  acetylene. 

(11)  Notice  to  be  fixed  on  the  generator  house  door — "  No  naked 
lights  or  smoking  allowed." 

(12)  No  repairs  to,  or  alterations  in,  any  part  of  a  generator, 
purifier,  or  other  vessel  which  has  contained  acetylene  shall  be 
commenced,  nor,  except  for  recharging,  shall  any  such  part  or  vessel 
be  cleaned  out,  until  it  has  been  completely  filled  with  water,  so  as  to 
expel  any  acetylene  or  mixtures  of  air  and  acetylene  which  may 
remain  in  the  vessel  and  may  cause  a  risk  of  explosion. 

Having  described  various  forms  of  the  items  which  go  to  form 
a  well-designed  acetylene  installation,  it  may  be  useful  to  recapitu- 
late briefly,  with  the  object  of  showing  the  order  in  which  they  should 
be  placed.  From  the  generator  the  gas  passes  into  a  condenser  to 
cool  it  and  remove  any  tarry  products.  Next  it  enters  a  washing 


SELECTION  AND  INSTALLATION  81 

apparatus  filled  with  water  to  extract  water-soluble  impurities. 
If  the  generator  is  of  the  carbide-to-water  pattern,  the  condenser 
may  be  omitted,  and  the  washer  is  only  required  to  retain  any  lime 
froth  and  to  act  as  water  seal  or  non-return  valve.  If  the  generator 
does  not  wash  the  gas,  the  washer  must  be  large  enough  to  act  effi- 
ciently as  such,  and  between  it  and  the  condenser  should  be  put  a 
mechanical  filter  to  extract  the  dust.  From  the  washer  the  acety- 
lene travels  to  the  holder.  From  the  holder  it  passes  through  one 
or  two  purifiers,  and  then  travels  to  the  drier  and  the  filter.  If  the 
holder  does  not  throw  a  constant  pressure,  or  if  the  purifier  and  the 
drier  cause  irregularities,  a  governor  or  regulator  must  be  added 
to  the  drier.  The  acetylene  is  then  ready  to  enter  the  service. 
When  the  gas  generally  leaves  the  generator  house,  a  full- way  stop- 
.  cock  must  be  put  in  the  main. 

Generator  Residues. 

According  to  the  type  of  generator  employed,  the  waste  product 
removed  therefrom  varies  from  a  moist  powder  to  a  thin  cream  or  milk 
of  lime.  Any  waste  product  which  is  quite  liquid  in  its  consistency 
must  be  completely  decomposed  and  free  from  particles  of  calcium 
carbide  of  sensible  magnitude.  In  the  case  of  more  solid  residues, 
the  less  fluid  they  are  the  greater  is  the  improbability  (or  the  less 
is  the  evidence)  that  the  carbide  has  been  wholly  spent  with  the 
apparatus.  Imperfect  decomposition  of  the  carbide  inside  the 
generator  not  only  means  an  obvious  loss  of  economy,  but  its  pres- 
ence among  the  residues  makes  careful  handling  of  those  essential 
to  avoid  accidents,  owing  to  a  subsequent  liberation  of  acetylene 
in  some  unsuitable  and,  perhaps,  closed  situation.  A  residue  which 
is  not  conspicuously  saturated  with  water  must  be  taken  out  of  the 
generator-house  into  the  open  air  and  flooded  with  water,  being  left 
in  some  uncovered  receptacle  for  a  sufficient  time  to  ensure  all  the 
acetylene  being  drawn  off.  A  residue  which  is  liquid  enough  to 
flow  should  be  run  directly  from  the  draw-off  cock  of  the  generator 
through  a  closed  pipe  to  the  outside,  where,  if  it  does  not  discharge 
into  an  open  conduit,  the  waste  pipe  must  be  trapped,  and  a  ventila- 
ting trap  provided  so  that  no  gas  can  blow  back  into  the  generator- 
house. 

As  the  acetylene  is  now  brought  through  in  the  mains,  it  will 
be  distributed  to  the  operators  through  an  hydraulic  safety  valve 
and  rubber  tubing  to  the  blowpipes.  It  is  usual  to  fix  the  main 
piping  overhead,  from  which  pipes  are  suspended,  at  specified  dis- 
tances, upon  which  pipes  are  attached  an  hydraulic  safety  valve. 

6 


82  MODERN  METHODS  OF  WELDING 

It  is  necessary  for  each  welder  to  have  one  hydraulic  safety  valve, 
or  water  seal,  for  each  blowpipe.  There  should  be  welding  tables 
or  benches  fixed  running  under  the  main  piping.  These  tables 
or  benches  are  generally  constructed  of  iron  or  steel  frames,  with 
boiler-plate  tops,  and  are  made  wide  enough  to  allow  welders  to  work 
opposite  each  other,  therefore  economising  space.  The  arrangement 
of  hydraulic  safety  valves  is  suspended  from  the  main  pipe,  above , 
the  centre  of  the  welding  table,  making  it  convenient  and  handy 
for  the  operators. 

The  next  operation  is  to  fill  all  the  hydraulic  safety  valves  with 
water  until  it  runs  out  of  the  water-level  test  cock.  When  this  has 
been  done,  the  rubber  tube  may  be  fixed  to  the  outlet  tap  of  the 
hydraulic  safety  valve  at  the  one  end,  and  the  blowpipe  at  the 
other  end.  Then  another  piece  of  tubing  is  taken  and  fixed  on  to 
the  regulator  (which  is  already  fixed  into  the  cylinder  valve); 
the  other  end  of  the  tubing  to  be  fixed  on  to  the  oxygen  tap  of  the 
blowpipe.  All  is  now  ready  for  .the  gases  for  welding.  The  acety- 
lene should  be  turned  on  at  the  main  cock  or  tap.  After  the  genera- 
tor has  been  charged  with  a  proper  quantity  of  calcium  carbide, 
the  holder  filled  with  water,  and  the  purifier  charged,  all  should  be 
ready  for  the  acetylene  to  be  let  into  the  main  piping.  Pure  acety- 
lene will  not  come  through  to  the  blowpipe  on  the  first  starting  up 
of  the  plant,  owing  to  a  quantity  of  air  in  the  piping  and  bell, 
which  has  to  be  replaced  by  the  acetylene  as  soon  as  generation 
takes  place.  Before  starting  generation,  all  the  taps  or  cocks 
fixed  in  the  main  pipes  should  be  left  open  to  allow  the  air  to 
escape  as  the  acetylene  starts  to  come  through ;  as  the  acetylene 
has  a  very  pungent  smell,  it  can  soon  be  observed  when  it  begins 
to  come  through  in  quantities.  As  soon  as  this  period  arrives,  the 
taps  can  all  be  shut  off,  and  the  blowpipe  lit.  The  oxygen  bveing  on 
at  the  cylinder  and  regulator,  and  acetylene  turned  on  at  the 
hydraulic  safety  valve,  and  then  the  two  taps  on  the  blowpipe — 
the  oxygen  first  and  the  acetylene  after  the  blowpipe  is  lit — allow 
it  to  burn  until  a  good  white  rigid  cone  appears.  This  will  take 
some  time,  owing  to  the  fact  that  at  first  starting  up  (as  already 
explained)  the  main  piping  is  partly  full  of  air,  although  the 
taps  on  the  main  piping  have  been  previously  opened.  This  air 
mixes  with  the  acetylene,  ignites  at  the  tip  of  the  blowpipe,  and 
gives  a  bluish  flame  almost  like  a  Bunsen  burner.  The  blowpipe 
is  to  remain  lighted  until  the  flame  reaches  a  small  violet-whitish 
jet  of  very  clear  outline,  when  it  will  indicate  that  the  air  is  all  out 
of  the  piping,  and  welding  may  be  done. 


CHAPTER  XVI 
METHODS  OF  WELDING 

THE  subject  to  which  we  are  now  about  to  proceed  is  one  which  should 
be  very  interesting  to  welding  operators.  My  experience,  through- 
out years  of  instruction  of  operators,  is  that  they  invariably  want 
to  handle  a  blowpipe  before  they  have  even  the  smallest  information 
of  welding  or  what  it  means.  They  soon  find  out,  however,  that  it 
is  best  to  start  from  the  beginning. 

With  all  appliances  in  order,  and  the  blowpipe  chosen,  work  can 
be  proceeded  with.     The  pieces  to  be  welded  consist  of  two  pieces  of 
angle  iron,  which  are  put  on  the  top  of  the  loose  bricks  on  the  weld- 
ing table.     The  hydraulic  safety  valve  is  tested.  fThe  acetylene  ga~s~T 
is  turned  on  at  the  tap  of  the  safety  valve  (the  taps  on  the  blowpipes  \ 
being  closed),  then  the  taps  on  the  regulator  and  the  blowpipe  are    \ 
both  opened  and  left  open.     The  cylinder  valve  is  open  to  let  the     [ 
oxygen  through  to  the  blowpipe.     The  oxygen  should  be  turned      \ 
off  temporarily  on  the  regulator  until  everything  is  ready  and  com- 
plete for  welding,  then  the  blowpipe  may  be  lit,  and  the  flame  regu- 
lated, j  The  blowpipe  should  be  held  in  the  hand,  in  the  central 
position  found  by  balancing.     The  weight  of  the  rubber  tubes  will, 
make  the  blowpipe  feel  balanced  and  light  in  the  hand. 

When  commencing  welding,  the  blowpipe  should  be  pointing_to_- 
the  line  of  welding  at  a  slight  angle,  so  that  the  blowpipe  will  melt 
the  metal  in  advance  of  the  tip  of  the  flame.     One  must  not  hold  it 
at  too  large  an  angle,  otherwise  the  molten  metal  will  be  blown  on 
the  cold  surface.     This  point  or  tip  of  the  flame — that  is,  the  clear •.„ 
white  cone — must  not  touch  the  metal,  but  must  be  about  i  inch 
from  it.     This  prevents  oxidisation  of  the  metal,  and  also  prevents 
the  nozzle  of  the  blowpipe  from  being  filled  up  with  metal  which  is 
blown  up  with  sparks.     Further,  a  much  neater  weld  is  made  with 
the  flame  above  the  molten  mass  than  in  it. 

The  blowpipe  should  be  held  freely  in  the  hand,  and  the  weld 
approached  at  one  edge,  care  being  taken  that,  as  soon  as  the  point 
of  melting  has  been  reached,  the  blowpipe  shall  be  moved  slowly  for- 
ward to  melt,  say,  J  inch  from  the  edge.  After  the  melting  of  this 

83 


84  MODERN  METHODS  OF  WELDING 

second  part,  the  blowpipe  should  be  instantly  passed  over  the  edge 
to  weld  this,  which  process,  from  the  previous  heating,  should  be 
almost  instantaneous.      The  object  of  heating  the  edge  first  and 
not  welding,  is  to  stop  the  molten  metal  from  running  from  the  edge. 
Nearly  all  operators,  when  learning,  make  this  mistake.     If,   as 
directed,  the  second  part  is  made  molten  and  welded,  and  then  the 
blowpipe  is  brought  over  to  the  end  of  the  weld,  this  becomes  molten, 
the  blowpipe  is  moved  to  the  third  position,  the  film  on  the  edge 
of  the  plate  is  not  broken.     Hence  it  supports  the  molten  of  the 
edge  which  has  been  done  at  the  second  heating.     When  proceeding 
with  the  welding  the  blowpipe  must  be  moved  forward  very  slowly, 
with  a  gyratory  movement.     The  progress  must  be  regular  and  con- 
tinuous, so  that  the  welding  may  be  even  and  quickly  done;  and 
Ixcare  must  be  taken  that  no  welding  shall  be  gone  aver  twice,  as  each 
time  it  is  done  the  metal  loses  some  of  its  most  important  constituents 
and  it  is  therefore  burnt  and  weak.    'If  it  is  necessary  that  the  two 
edges  of  the  article  that  is  being  welded  shall  be  made  molten 
together,  the  welding-rod  used  must  also  be  in  the  same  molten 
mass  together.     If  the  welding-rod  is  kept  in  close  proximity  to  the 
cone  of  the  flame,  unity  of  fusion  of  both  the  edges  of   the  weld 
and  the  welding -rod  will  take  place,  leaving  an  homogeneous  Weld. 
-7$Clt  is  best  to  train  the  hand,  when  engaged  on  small  work,  To 
make  the  flame  of  the  blowpipe  describe  an  elliptical  movement, 
the  longer   diameter  corresponding   to  double  the  width   of   the 
section  of  the  article  being  welded.     Also,  at  the  same  time  that  this 
is  being  performed,  it  is  necessary  to  combine  with  this  elliptical 
motion  an  advancing  one ;  and,  in  the  advancing,  one  must  keep  to 
the  centre  line  of  welding.     In  the  welding  of  thick  plates,  where 
the  article  is  either  bevelled  on  one  side  or  on  both,  the  same  ellipti- 
cal and  advancing  movement  as  for  light  work  is  required;  but  a 
welding-rod  is  to  be  used  constantly  and  regularly,  so  as  to  fill  up 
the  part  that  has  been  bevelled.     In  articles  more  than  f  inch  thick 
two  layers  have  to  be  put  on,  one  after  the  other,  otherwise  a  sound 
weld  could  not  be  secured. 

The  welding-rod  is  held  and  directed  by  the  left  hand,  and  should 
be  suspended  between  the  top  of  the  two  fingers  and  the  thumb, 
and' over  the  side  of  the  hand,  almost  as  one  holds  a  pen.  It  will  be 
found  that  the  rod  will  thus  be  balanced  nicely  for  working  with 
accuracy  under  the  tip  of  the  cone.  The  thickness  of  the  welding-rod 
should  be  in  proportion  to  the  thickness  of  the  article  to  be  welded. 
It  is  very  important,  ae  previously  stated,  that  the  melting  of  the 
feeding-rod  and  the  edges  of  the  weld  should  take  place  at  the  same 


METHODS  OF  WELDING 


85 


time,  so  as  to  make  the  edges  of  the  article  and  the  feeding-rod  com- 
bine and  form  one  solid  metal.  Particular  care  must  be  taken  to 
prevent  the  flowing  metal  from  the  rod  falling  on  the  unwelded  edges 
of  the  article.  This  would  cause  the  weld  to  be  defective.  It  would 
be  adhesion,  not  a  weld.  This,  although  so  simple  an  error,  is  often 
committed,  even  by  experienced  welders.  More  care  ought  to  be 
taken  not  to  let  these  simple  errors  occur.  No  matter  how  well 


FIG.  31. — BUTT  JOINT. 

the  other  part  of  the  weld  is  finished,  if  there  is  a  defect  like  that  of 
adhesion,  it  ruins  the  whole  weld.  In  testing,  the  least  sectional 
area  will  be  taken.  Therefore,  if  the  article  is  |  inch  thick,  and  adhe- 
sion is  carried  for  J  inch  deep,  the  weld  is  only  half  as  strong.  The 
smallest  sectional  area  is  J  inch  thick,  whereas  the  article  is  \  inch 
thick,  being  a  loss  of  strength  of  50  per  cent.  Operators  should 


FIG.  32. — INDENTS,  NOT  SUFFICIENT  WELDING-ROD  ON. 

make  these  small  tests  themselves,  as  this  is  the  quickest  and  surest 
method  of  finding  out  their  own  defects. 

The  operator  should  make  the  rod  melt  at  the  same  time  as  the 
welded  edges.  The  rod  is  kept  in  the  proximity  of  the  flame,  at 
almost  melting-point,  so  that,  as  the  two  edges  become  melted,  the 
rod  is  put  or  dropped  on  to  the  molten  mass,  by  passing  just  through 
the  cone;  and,  as  the  welding  proceeds  at  a  uniform  speed,  the  rod 
is  progressively  worked  at  a  sufficient  rate  of  melting,  to  fill  up  the 
gap  in  the  bevel  and  to  complete  the  level  of  the  weld  to  the  same 
thickness  as  the  article  being  welded.  If  operators  will  keep  in 


86  MODERN  METHODS  OF  WELDING 

mind  the  information  given  so  far,  they  should  have  some  idea  as  to 
the  melting  of  the  article,  to  the  mixing  and  the  forming  of  the 
molten  mass  before  solidification,  and  to  the  use  of  the  blowpipe. 
They  should  be  able  to  grasp  the  principle  of  the  execution  of  welds ; 
but  more  practice  and  more  study  are  necessary  to  make  proficient 
welders. 

Homogeneous  welding  is  the  union  of  bodies  by  fusion.  Usually 
the  operator  does  not  melt  enough,  does  not  get  the  edges  molten 
before  he  lets  the  molten  rod  fall  on  the  unwelded  surface.  Or  he 
makes  holes,  and  tries  to  fill  them  up  by  adding  the  feeding-rod, 
which  usually  drops  on  the  cold  surfaces.  But  by  quiet  determined 
tuition  and  practice  the  student  soon  comes  to  know  what  are 
the  defects  and  makes  great  effort  to  remedy  them.  He  must  prac- 
tise every  form  of  welding,  but  must  first  of  all  master  the  commonest 
joints,  such  as  the  butt  and  the  edge.  These  joints  must  be  done 
over  and  over  again  before  he  is  allowed  to  proceed  with  further 
kinds  of  welds.  This  is  imperative  if  he  intends  to  become  a  first- 
class  operator.  Two  joints  should  be  made :  first,  weld  with  welding- 
rod  ;  second,  without  welding-rod  ;  third,  with  welding-rod,  hammer, 
and  anneal. 

The  two  tests  should  be  butt  and  edge,  and  ^-inch  thick  steel. 
"  Bending  test "  may  be  made  by  fixing  in  the  vice  the  article 
welded  with  the  line  of  the  weld  just  -J  inch  above  the  vice,  then 
bend  right  over  with  a  hammer.  "  Area  test " :  Two  pieces  put  at 
right  angles,  and  weld  along  the  corner,  seam,  then  flatten  out  with 
hammer ;  see  if  the  area  is  the  same  thickness  as  the  material  welded . 
Third  test:  Two  pieces  J  inch  thick;  butt  and  weld;  use  plenty  of 
welding-rod.  After  welding,  heat  the  piece  up  to  white  heat  by 
blowpipe,  hammer  to  thickness  of  metal ;  repeat  the  heating  by  the 
blowpipe,  and  allow  to  cool;  and  then  bend  in  the  vice.  Watch 
the  difference  between  the  annealed  one  and  the  one  not  annealed. 
If  these  tests  fracture  when  bent,  repeat  the  welding  and  testing  of 
these  two  articles  until  they  can  be  done  without  cracking  or  fracture. 

Operators  in  the  first  few  courses  of  training  generally  point  the 
flame  on  to  one  of  the  faces  of  the  bevel.  As  the  metal  melts  it 
runs  down  on  the  other  "  cold  "  side.  It  is  usually  covered  over 
by  the  molten  metal,  and  is  not  seen  externally;  but  the  defect  is 
there,  nevertheless.  Operators  must  not  allow  this  to  occur,  but 
must  remember  that  the  simultaneous  and  regular  melting  of  the 
two  edges  of  the  weld  and  the  welding-rod  is  a  very  important  point. 
If  good  welds  are  to  be  obtained,  this  is  a  sine  qua  non.  The  begin- 
ning of  the  weld  is  always  slower,  and  the  end  more  rapid,  because  the 


METHODS  OF  WELDING 


87 


temperature  of  the  article  is  increased  as  the  line  of  welding  reaches 
the  end.  The  finishing  must  be  done  sharply,  otherwise  the  metal 
gets  so  molten  that  the  ends  give  way  and  allow  the  molten  metal 
to  run  away. 

We  may  now  proceed  to  autogenous  problems.  The  vast  amount 
of  welding  carried  through  during  the  war  was  really  amazing.  The 
thousands  engaged  on  this  process  were  chiefly  concerned  with 
mild  steel  articles  for  military  purposes.  Millions  of  feet  of  sheet 


FIG.  33. — ROUND  BAB  BEVEL,  CHISEL  POINTS. 

steel  were  welded,  and  the  task  of  training  these  temporary  operators 
was  huge.  Of  course,  there  was  no  time  to  impart  a  thorough  know- 
ledge of  welding.  They  were  given  just  sufficient  instruction  to  enable 
them  to  get  along  and  practise  for  themselves.  It  was  remarkable, 
however,  how  quickly  they  settled  down  to  the  plain  welding  of  mild 
steel  articles.  These  welds  apparently  are  the  most  easy  to  obtain, 
but  in  reality,  to  do  them  as  they  ought  to  be  done,  so  that  they  will 


/\ 


FIG.  34.— TUBE  BEVEL. 

stand  any  test  applied,  is  not  so  easy.  Indeed,  they  require  on 
the  part  of  the  operator  the  utmost  thought  and  care.  It  is 
well  known  that  90  per  cent,  of  welding  is  in  mild  steel,  therefore 
the  operator  will  have  to  be  taught  the  constituents  and  analysis 
of  these  metals.  He  must  also  make  himself  acquainted  with  the 
melting-points  of  the  metals  and  their  oxides.  He  must  study  the 
articles  on  the  different  metals  in  other  parts  of  this  book,  and  must 
especially  learn  to  know  the  melting-points  of  all  metals  and  their 
oxides.  This  is  most  important  in  the  cases  where  the  metals  and 
their  oxides  differ  in  their  melting-points.  Take,  for  instance,  steel 


88 


MODERN  METHODS  OF  WELDING 


and  aluminium.  Steel  is  1,600°  C.,  aluminium  700°  C.  In  the  case 
of  the  oxides  the  difference  is  very  much  greater.  Aluminium  melts 
at  700°  C.,  but  its  oxide  melts  at  1,600°  C.;  this  is  why  operators 
do  not  find  aluminium  welding  easy  of  execution.  The  metal  itself 
readily  forms  in  globules  or  beads,  which  do  not  run  together 
owing  to  the  outside  film  not  being  melted.  These  films  are  the 
oxide.  The  same  happens  to  all  metals,  but  others  are  not  so  much 
djefined  as  aluminium. 

There  are  many  defects  that  happen  in  welding  which  could  be 
avoided  if  operators  would  see  if  they  were  corrected  as  they  went 
along.  Some  of  the  defects  in  welding  mild  steel  will  be  described 
below. 

The  first  is  the  lack  of  penetration — that  is,  either  the  power  of 
the  blowpipe  has  not  been  large  enough  or  the  operator  has  passed 


FIG.  35. — FRACTURE  AFTER  BENDING.       FIG.  36. — LACK  OF  PENETRATION. 

over  the  line  of  welding  far  too  fast.  This  lack  of  penetration  is  a 
serious  defect,  and  is  a  defect  that  is  commoner  than  any  other, 
especially  in  the  case  of  butt  welding.  By  not  penetrating  right 
through  the  metal,  the  original  thickness  of  the  metal  is  reduced 
in  sectional  area,  because  the  weld  has  only  penetrated  to  two-thirds 
of  its  thickness.  This  is  very  serious,  and  in  the  case  of  tubing  which 
has  to  stand  pressure  very  often  the  weld  gives  before  the  full 
pressure  is  put  on.  This  non-penetration  occurs  sometimes  when 
the  edges  are  not  bevelled.  The  heat  has  not  been  sufficient  for 
the  fusion  to  go  right  through  the  whole  thickness  of  the  joint, 
and  also  the  thickness  not  welded  constitutes  a  starting-point  for 
a  break. 

Figs.  35  and  36  show  the  weld,  and  the  result  of  the  bending. 

On  the  other  hand,  operators  should  take  care  not  to  penetrate 
too  far  through,  or  the  metal  runs  through  from  the  molten  bath 
above,  and  often  leaves  a  conical  hole  which  is  difficult  to  fill  up  and, 
in  doing  so,  generally  oxidises  the  metal  owing  to  being  too  long  on 
the  weld,  and  the  metal  is  burnt. 


METHODS  OF  WELDING 


89 


Adhesion  is  another  defect  which  operators  often  make,  especi- 
ally in  thick  bevelled  work,  owing  either  to  not  having  a  powerful 
enough  blowpipe  or  to  too  heavy  a  pressure  of  oxygen,  which 
"  swills  "  the  surface  of  the  bevel,  without  taking  time  to  make  it 
liquid;  dropping  the  liquid  rod  on  this  "swilled"  surface  causes 
it  to  stick  or  adhere.  This  is  not  fusion.  Then,  again,  some  opera- 
tors do  not  melt  both  edges  together,  and  therefore,  again,  no  fusion 
or  unity  takes  place.  Again,  many  welds  are  interposed  with  oxide. 
This  arises  from  several  causes.  The  metal  may  not  have  been 
properly  liquefied,  which  causes  blowholes  to  form  in  the  interior 
of  the  molten  mass  and  remain  after  solidification.  Likewise,  if  the 
metal  gets  too  hot  and  boils,  this  causes  gas  to  be  imprisoned  in  the 
interior  of  the  weld,  also  producing  blow-holes.  The  defect  may 
also  arise  from  not  attacking  the  bevelled  edges  of  the  weld  suffi- 


FIG.  37. — SINGLE  BEVELLED  JOINT. 


FIG.  38. — ADHESION,  BAD  WELD. 


ciently,  or  attacking  them  unequally,  or  from  the  flowing  of  the 
metal  or  the  liquid  welding-rod  on  the  edges  that  have  not  been 
melted. 

Operators  must  pay  attention  to  this  point  and  understand  that 
the  molten  metal  flowing  from  the  edge  of  the  weld  brings  about 
adhesion  if  this  part  itself  is  not  melted.  It  is  very  important 
indeed  that,  before  the  bevelled  edges  are  melted,  the  bottom  of  the 
bevel  should  be  melted  first,  so  that  as  the  sides  of  the  bevel  are 
melting,  the  liquid  metal  runs  into  the  molten  bath  lying  ready  to 
receive  it  at  the  bottom  of  the  bevel.  If  this  is  carried  out  there 
will  be  no  adhesion. 

It  is  important  that  all  welds,  no  matter  for  what  job,  should 
always  be  well  filled.  There  must  be  no  part  of  the  weld,  on  either 
side,  under  the  full  section  of  the  metal  which  is  being  welded. 
If  it  is,  the  article  loses  its  strength.  This  is  almost  as  much  to  be 
avoided  as  a  bad  weld.  Assume  a  tube  is  being  welded  J  inch  thick. 
A  butt  joint  is  being  made,  and  it  is  welded  along  the  line  of  the 


90 


MODERN  METHODS  OF  WELDING 


weld  with  what  is,  from  the  operator's  point  of  view,  a  good  weld. 
It  is  inspected  and  found  to  have,  in  two  or  three  places  along  the 
outside  lines,  indents  about  •£$  inch  deep.  These  indents  were  caused 
by  the  melting  of  the  original  metal,  which  flowed  with  the  circular, 
movement  of  the  blowpipe,  and  left  the  indents  behind.  These 
should  have  been  filled  up  with  the  welding-rod  as  the  welding  pro- 
ceeded. Consequently,  through  this  error,  the  tubing  will  not  stand 
the  full  amount  of  test  designed  for  J  inch  thick.  The  finished 
sectional  area  is  only  ^V  inch  thick.  If  ^  would  do,  why  use  J  inch 
thick  ?  Operators,  however,  must  learn  to  keep  the  welds  up  to 
the  thickness  of  articles.  These  articles  are  skilfully  designed  and 
the  stresses  all  calculated  out  for  the  purposes  to  which  they 
are  to  be  put;  therefore,  if  the  welding  all  over  is  not  up  to  that 


First  Start 
of  Fracture 


\ 


FIG.  39. — NOT  FULLY  PENETRATED, 
FIEST  STARTING  OF  FRACTURE. 


FIG.  40. — NOT  PENETRATED  THROUGH. 


particular  thickness  the  article  is  not  so  strong.  In  some  cases 
this  is  important. 

Tests  for  Welds. — The  majority  of  defects  are  hidden  in  the  body 
of  the  weld,  and  the  operator  is  often  ignorant  of  them.  But  there 
are  many  ways  of  testing  welds,  so  that  after  he  finds  them  out 
he  should  be  able  to  overcome  all  his  defects.  This  will  take  some 
time,  but  with  patience  and  close  study  he  should  be  successful. 
One  cannot,  of  course,  break  joints  of  commercial  work  in  order  to 
get  stresses  and  strains  or  examine  the  internal  constitution.  But 
with  facilities  to  make  his  own  test-pieces  of  similar  metal  to  those 
he  has  worked  with,  the  operator  is  able  to  make  all  the  tests  neces- 
sary, including  resistance  and  elongation.  Test  by  corrosion,  or, 
as  it  is  called,  the  micrographic  test,  may  be  applied  to  all  metals 
of  yF  m°h  or  over. 

Two  pieces  of  flat  bar  should  be  welded,  about  3  inches  long, 
butt- join  ted,  and  then  cut  through  the  longitudinal  way,  across  the 
weld.  One  of  the  faces  is  to  be  polished  to  a  spotless  surface,  all 


METHODS  OF  WELDING 


91 


grease  is  removed,  and  the  etching  fluid,  applied  with  a  brush, 
soon  exposes  any  defect,  adhesion,  or  oxide.  A  plain  black  image 
appears  which  shows  all  flaws  very  plainly,  and  if  it  has  been  burnt 
this  also  can  be  clearly  seen.  It  is  important  that  the  face  be  polished 
well  and  free  from  grease.  The  polishing  does  not  disclose  any 
defect,  unless  it  be  a  bad  one;  but  when  the  etching  fluid  is  applied, 
the  defects  appear  instantly.  Therefore,  if  operators  will  from  time 
to  time  practise  these  tests,  they  will  soon  remedy  the  defects. 


FIG.  41. — BENDING  A  TEST-PIECE  IN  A  VICE. 

Etching  liquid  may  be  as  follows : 

Iron  and  steel 

(water     . .          . .  10  parts. 
Iodine  solution  j  potassium  iodine    2     ,, 

(iodine     . .          . .     1  part. 

The  solution  is  applied  with  a  brush  immediately  the  polished 
cut  is  ready.  The  structure  develops  almost  suddenly,  and  in  a 
few  minutes  the  corrosion  is  sufficient.  Wash  with  running  water, 
dry  with  alcohol,  and  cover  with  a  layer  of  varnish  if  the  test  is  to 
be  preserved.  The  test  by  bending  is  one  applied  in  most  technical 
schools,  and  is  appropriate  for  all  ductile  metals.  A  test-piece  may 
be  made  out  of  f-inch  diameter  round  steel.  This  must  be  first 
prepared  for  welding  by  shaping  two  ends  to  chisel  type  ends. 
The  reason  why  it  must  be  pointed  as  a  chisel  is  that,  as  the  metal 
is  welded,  it  falls  down  to  the  bottom  where  the  chisel-point  meets, 
at  the  centre  of  the  round  bar.  If  it  were  not  for  the  chisel-point,  the 


<)2  MODERN  MKTllons  or  \vi«:u>lN<! 

article  heini'  round,  I  lie  tnel;d  would  run  to  the  bottom  of  <  ho 
welding  table  ;uid  sprea.d  about  instead  of  building  U|>.  Tin-  welding 
of  I. hi:;  round  piece  should  In-  executed  and  finished  off  (lie  sa.mo 
thickness  as  the  bar  itself,  so  as  to  give  it  a,  lair  lest  \\hni  hcndinir; ; 
allcr  welding  and  cooling  it  can  be  put  in  the  vice,  \\ilh  1  IK-  \\<  Id 
just  o\  <T  Mir  lop  of  Ihc  ja.ws,  the  hammer  applied  in  any  direr!  ion. 
It  should  be  bent  over  to  a  radius  of  1J  inches.  If  Mi  is  is  done 
without  a  eraek  or  fracture,  tin-  work  \\ill  pass. 

Tho  hammerim:  ;uid  annealing  test  is  the  best  of  all.  Operator.-: 
should  weld  srvrral  of  tlicsti  sniitll  test  pie<  e  ;  in  various  sections  of 
steel.  Ono -third  of  the  tost  pieces  to  he  put  through  the  three 
tests  of  corrosion — bonding,  hammering,  and  annealing  should  he 
pieces  whore  welding  only  has  been  done;  one  third  should  he  pieces 

which  have  been  welded,  annealed,  and  hammered;  annealed  and 
cooled  slowly.     A  record  of  all  thcso  tests  should  he  kept,  and  the 
result  will  bo  surprising.     The  illustration  (Fig.  41)  shows  a  1< 
piece  in  a  vice;  this  is  a  very  easy  method  of  the  bonding  I- 
students  who  oan  execute  welds  to  stand  this  test  should  he  able  to 
tackle  all  ordinary  commercial  work. 


CHA1TKK  XVII 
PREPARATION  OF  WELDS 

1 '  J  impo  ible  to  own- stimate  the  importance  of  thorough  pre- 
paration of  I  IK  work  before  the  weld  is  actually  attempted.  Any 
time  spent  in  this  way  is  amply  repaid  afterwards  in  the  easier 

•u!  ion  thus  made  possible.  The  preparation  varies  considerably 
with  the  nature  of  the  metal  and  the  thickness  and  form  and  posi- 
tion of  the  parts  or  articles  to  be?  welded.  It  is  impossible  to  lay 
down  any  hard-and-fast  rules.  Tor  e;u-h  metal  we  may  have  to 
adopt  a  different  preparatory  procedure.  For  instanee,  some,  of 
the  m<-tals  have  mueh  lower  melting  points  than  others,  and  must 
be  dealt  with  accordingly. 

The  general  principles  obtaining  in  the  best  practice  direct 
that  the  lino  of  weld  must  be  opened  out — that  is,  the  two  sides 
bevelled,  each  to  45  degrees,  making  an  angle  of  90  degrees.  This 
i  >  o  make  certain  that  the  weld  shall  be  penetrated,  and  not  merely 
sealed  over.  The  welding  must  be  done;  from  the  bottom  of  the 
bevel  and  properly  filled  in  with  the  welding-rod,  the  metal  at  the 
edges  being  molten  at  the  same  time,  so  as  to  unite  with  the  molten 
rod;  the  two  combining  make  a  good  sound  weld.  Bevelling  also 
increases  the  area  of  the  surface  of  the  weld,  thereby  strengthening 
the  latter.  It  allows  the  addition  of  a  larger  quantity  of  metal  of 
better  quality,  since  rods  of  pure  iron  are  added  to  the  welds. 
Bevelling  is  carried  out  on  thicknesses  of  i  inch.  After  it 
reaches  J  inch  and  over  in  thickness,  the  bevel  should  be  on  both 
The  illustrations  on  p  !M  show  two  pieces. 

It  is  essential  that  the  line  of  welding  should  be  thoroughly 
elearic'J    (particularly  in  the  case  of  aluminium),   either   by   hand 
tools  or  by  some  ehemieal  agent.     Too  much  stress  cannot  be  put 
on  this,  as  welders  often  find.     The  mo  t  important  part  of  the  pre- 
paration is  that  of  arranging  the  pieces  to  be  welded  in  such  a  p<>  i 
lion  that  then-,  will  be  no  deformation,  fractures,  cracks,  or  internal 

in  and  that  they  will  he  linablc  at  the  coneln  -ion  of  the  opera- 
tion. This  applies  ehieMy  to  casl  iron  artiele-:,  \\hieh  are  generally 


94  MODERN  METHODS  OF  WELDING 

intricate  castings  of  various  thicknesses  and  irregular  shapes  and 
are  often  cumbersome. 

This  is  a  point  in  which  the  skill  of  the  operator  is  revealed, 
as  there  are  no  fixed  rules  to  guide  him.  Welders  too  often  fail 
to  take  sufficient  precautions  to  keep  the  article  adjusted  and  in  a 
correct  position  for  welding,  so  as  to  allow  for  that  phenomenon 
known  as  expansion  and  contraction,  and  to  leave  the  welded  article 
Unable  at  the  finish.  One  must  keep  in  mind  that  old  maxim: 


FIG.  42. — FLAT  BAR  DOUBLE  BEVEL. 

"  What  is  worth  doing  is  worth  doing  well."  A  weld  well  prepared 
is  half  done.  As  the  result  in  welding  depends  to  a  certain  degree 
on  how  the  preparation  has  been  carried  out,  one  cannot  spend  too 
much  on  it,  especially  where  intricate,  uneven  castings  are  concerned. 
It  is  the  interested,  careful,  and  thoughtful  workman  who  gets  success 
in  the  welding  of  such  articles. 

Bevelling  should  be  done  on  both  sides,  as  has  been  said,  if  over 


I 

1 

FIG.  43. — ANGLE  IKON,  BEVELLED  ONE  SIDE. 

J  inch  thick.  If  it  cannot  be  got  from  both  sides,  then  a  deeper 
bevel  must  be  made  on  the  one  side.  Operators  sometimes  do  not 
bother  about  bevelling,  even  if  it  is  a  case  of  \  inch  thick  without 
bevelling.  To  omit  it  always  leads  to  bad  results — such  as  bad 
psnebration,  adhesion,  or  overheating  of  the  metal — and  usually 
leaves  about  J  inch  unwelded  at  the  bottom  edge.  This  reduces 
ths  se3bional  area,  and  is  the  means  of  starting  a  fracture  (see 
the  illustrations  below),  which  is  what  happens  when  the  articles 
are  not  welded  through.  If  the  above  defective  weld  were  tested, 
it  would  hardly  stand  a  tensile  test  of  three-fifths  of  the  original 


PREPARATION  OF  WELDS 


95 


strength  of  the  metal.  Taking  a  good  view  of  the  above  section, 
one  sees  that  the  weld  does  not  touch  the  bottom  joint  of  the  bar. 
Further,  it  can  be  clearly  observed  that  the  molten  metal  did  not 
penetrate  through  the  full  thickness,  but  formed  itself  into  a  semi- 
iircular  mass  at  the  bottom  joint  of  the  bar.  This  semicircular 
line  reduces  very  much  the  area  of  the  weld,  and  with  it  the  strength. 
If  a  proper  weld  had  been  made,  a  f -inch  plate  would  have  been  quite 


V 


FIG.  44. — NOT  PENETRATED. 

as  strong,  and  a  great  saving  of  material  in  the  thickness  of  the 
respective  plates  would  have  been  effected.  In  the  illustrations  the 
lines  marked  A  and  B  show  the  thickness  of  the  metal  not  welded. 
This  is  a  great  consideration  from  an  engineer's  point  of  view.  He 
designs  work  calculated,  on  a  specified  thickness,  to  stand  certain 
stresses;  and  it  may,  in  any  particular  instance,  be  a  very  important 


Fia.  45. — SPACE  BETWEEN  A  AND  B  SHOWS  AMOUNT  UNWELDED,  AND  FRACTURE 

WHEN  BENT. 

job,  where  the  stresses  must  be  kept  up  to  counteract  the  design. 
But  if  a  bad  weld  is  made  and  does  not  penetrate  to  the  thickness, 
then  the  article  will  fail,  and  cause  heavy  loss.  On  the  other  hand, 
if  one  was  sure  of  always  penetrating  the  weld  (which  can  only  be 
done  by  preparing  and  bevelling),  articles  can  be  designed  with 
lighter  materials,  thus  saving  expense. 

Tho  above  sketches  show  very  clearly  how  defects  occur;  the 
welding  has  not  been  penetrated  through   the  whole  thickness. 


96  MODERN  METHODS  OF  WELDING 

hence  the  strength  is  not  up  to  the  thickness  of  the  original  metal. 
Upon  bending  the  bar,  the  unwelded  line  opened,  and  also  started  a 
fracture  along  the  line  of  welding. 

One  cannot  be  too  emphatic  in  stating  that  pure  metals,  pure 
welding-rods,  pure  gases,  are  most  essential  to  good  welds.  Adjust- 
ment before  welding  is  a  point  in  which  the  experience  and  skill  of 
the  operator  tells.  There  are  very  few  rules  for  his  guidance,  as 
the  articles  are  so  different  that  each  one  has  its  own  particular 
scheme.  Upon  any  work  but  that  of  the  simplest  character,  failure 
to  grasp  and  apply  the  laws  of  expansion  means  partial  or  total  ruin 
of  the  work.  It  is  impossible  to  control  expansion  and  contraction 


FIG.  46. — MACHINE  OPERATOR  WELDING  SEAMS  116  INCHES  LONG  IN  CORRUGATED 
SHEETS  FOR  TRANSFORMERS. 

by  physical  or  mechanical  forces.  The  only  way  to  prevent  disastrous 
results  is  to  foresee  the  probable  direction  and  extent  of  the  pheno- 
mena and  nullify  the  effect  by  preheating  the  whole  or  certain  parts 
of  the  work,  either  by  the  blowpipe  or  the  welder's  furnace,  the  latter 
being  recommended. 

Operators  must  take  precautions  with  all  articles  of  non-ductile 
metals,  to  see  that  they  are  all  properly  adjusted,  and  carefully 
fixed  at  some  part  of  them,  to  prevent  them  being  moved  or  dis- 
turbed during  the  process  of  welding.  They  must  provide  that  ex- 
pansion and  contraction  shall  take  place  uniformly,  so  that  the 


PREPARATION  OF  WELDS 


97 


article  is  not,  after  welding,  distorted  in  any  way  nor  out  of 
alinement.  There  are  various  ways  of  making  these  fixtures,  and 
a  series  of  different  sizes  should  be  kept.  One  is  illustrated  below, 
which  is  easily  manipulated,  even  when  hot  from  -the  furnace. 

Expansion  in  physics  is  an  enlargement  or  increase  in  the  bulk 
of  bodies,  in  consequence  of  a  change  of  their  temperature.  This 
is  one  of  the  most  general  effects  of  heat,  being  common  to  all  bodies 
whatsoever,  whether  solid  or  fluid.  The  expansion  of  solid  bodies 
is  determined  by  the  pyrometer.  One  can  realise  the  force  of  expan- 
sion from  water  "that  has  frozen  in  an  enclosed  vessel  or  pipe.  When 
the  careless  motorist  leaves  the  cooling  water  of  the  engine  in  the 
water-jacket  of  the  cylinder  overnight,  on  a  frosty  day,  the  next 


FIG.  47.— CASTING  BROKEN. 
Left:  Bevelled  and  cramped  setting  for  welding.     Right:  Welding  completed. 

morning  there*  may  be  ice.  On  which  heating  by  water  or  other- 
wise, the  ice  expanded,  and  this  powerful  force  fractures  the  cylinder 
water-jacket  owing  to  there  being  no  outlet  for  the  expansion. 

This  same  phenomenon  is  seen  with  all  cast-iron  articles.  It 
is  useless  to  attempt  by  force  to  oppose  this  expansion  and  contrac- 
tion. The  method  is  to  avoid  or  limit  the  consequences.  If  not, 
any  welding  done  on  non-ductile  articles  will  surely  cause  deforma- 
tion, cracks,  and  internal  strains.  The  whole  articles  should  be  raised 
to  a  temperature,  in  the  case  of  cast  iron,  of  not  less  than  900°  C.. 
and  not  exceeding  1,100°  C.,  and  then  quickly  welded,  and  returned 
to  the  annealing  furnace  to  cool  slowly. 

It  must  be  understood  that  there  is  no  other  means  of  obtaining 
good  results  on  non-ductile  articles,  except  that  of  preheating 'and 
annealing  on  properly  designed  and  well-thought-out  lines.  In  cases 

7 


98 


MODERN  METHODS  OF  WELDING 


45' Bevel 


\ 


Finished  weld. 


II 

Fig*  48.  Proper  set  up  For  butt 
welding  oF  pipe,  and  Finished 
weld. 


Bevel  here 


Section   showing 
Finished  weld.  / 


Fig.  49.  Welded  cross  in  pipe,  left, 
bevel  right,  welded. 


Bevel  here 


Section  showing 
Finished  weld.  ," 


50.  Showing  construction  oF 


T  pipe,  bevel  and  weld. 


Bevel  here. 

I 


Section  showing 
Finished  weld 


Fig.  51 .  Showing  pipe  at  45  degrees, 
weld  and  bevel. 


FIGS.  48  TO  51. 


PREPARATION  OF  WELDS  99 


where  the  articles  are  free  to  expand  and  contract  and  are  fairly  even 
in  thickness  and  size,  welding  may  be  done  without  preheating. 
These  articles  will  not  crack  when  welding;  but  they  are  few,  and 
should  be  carefully  watched.  After  welding  they  should  be  placed 
in  the  annealing  oven  to  remove  all  internal  strains,  and  left  to  cool 
slowly. 

The  illustration  on  p.  97  is  a  case  where  it  is  not  necessary  to 
take  expansion  into  consideration,  as  there  are  no  tied  ends.  The 
casting  may  therefore  be  welded  from  the  cold  state ;  but,  from  an 
economical  point  of  view,  it  should  be  heated  to  save  the  gas.  The 
illustration  referred  to  shows  how  a  casting  should  be  prepared  for 
welding.  The  line  of  bevelling  can  be  seen;  the  under  side  is 
similarly  bevelled ;  the  fixing  of  the  cramps  will  be  noted,  holding 
the  casting  in  position  while  the  welding  is  performed. 

In  making  the  set-up  for  butt-welding  pipes  the  edges  should  be 
separated  sufficiently  to  allow  the  heat  of  the  welding  flame  to  drive 
all  the  way  to  the  bottom  of  the  weld.  This  separation,  however, 
should  not  exceed  J  inch,  because  too  great  separation  is  conducive 
to  the  formation  of  large  bumps  of  metal  within  the  pipes,  which  is 
very  undesirable.  Many  operators  butt  the  edges  of  the  pipe 
"  square  up  "  and  do  not  attempt  to  secure  complete  penetration. 
The  weld  is  slightly  reinforced  and  is  virtually  as  strong  as  any  portion 
of  the  pipe.  The  edges  of  the  butt  weld  in  the  pipe  and,  more  par- 
ticularly, those  of  other  fittings  shown  herewith  should  be  bevelled 
Simple  as  these  lay-outs  appear,  the  average  operator  experiences 
more  or  less  difficulty  in  getting  the  various  parts  to  line  up  satis- 
factorily. 

Figs.  48  to  51  show  several  tube  joints,  described  above. 


CHAPTER  XVIII 
WELDING    TABLES 

SMALL  welding  tables  are  used  in  both  small  and  large  workshops. 
There  is  quite  a  variety  of  types,  from  which  one  may  select  any 
particular  one.  They  are  built  so  as  to  give  an  easy  position  to  the 
operator,  who  can  work  all  round  it. 

This  facilitates  the  task  very  much,  and  the  weld  is  done  quicker 
and  better.     The  tables  are  portable  and  can  be  moved  anywhere. 


FIG.  52. — MILD  STEEL  OPERATOR'S  TABLE. 

They  are  usually  constructed  of  angle-iron  formation,  and  all  the 
joints  are  welded.  They  may  be  light,  and  1J  by  ^  angle  steel  is 
strong  enough  for  all  ordinary  purposes.  The  making  is  quite 
simple,  being  a  matter  of  a  few  hours  for  any  intelligent  operator. 
Firstly,  there  are  two  frames,  say,  2'  9"  X  1'  9",  which  can  be 
made  in  one  piece ;  cut  a  V  out  of  each  corner ;  then  bend  at  those 
places  where  cut  out  and  weld  up.  Then  the  four  legs  should  be 
welded  to  the  frames,  the  one  of  which  is  on  the  top  of,  and  the  other 
inside,  the  legs,  8  inches  from  the  bottom.  This  bottom  frame  should 

100 


WELDING  TABLES 


101 


be  fitted  with  a  mild  steel  plate,  dropped  closely  into  the  angle  frame, 
forming  a  tool  table,  where  the  operator  can  keep  his  tools  and  weld- 
ing-rods. Tables  are  usually  made  2  feet  3  inches  high,  but  this  may 
be  altered  to  any  height. 

The  following  are  illustrations  of  ordinary  types,  but  they  may 
be  varied  to  suit  circumstances. 

One  of  them  is  shown  plain  and  one  with  fire-bricks.  Notice 
strips  welded  across  the  top  frame  to  carry  the  bricks;  the  other  is 
shown  with  fire-bricks  in  position.  It  is  very  necessary  for  fire- 
bricks to  be  put  under  articles  to  be  welded,  because  the  brick  retains 


FIG.  53. — ADJUSTABLE  WELDING  TABLE,  WITH  VICE  ATTACHED. 

the  heat,  which  assists  the  heating  of  the  articles  being  welded, 
thereby  saving  gas.  This  is  much  better  than  having  a  bare  steel- 
plate  table,  which  often  warps  by  the  continual  heating.  The  size 
of  the  top  may  be  determined  by  the  layer  of  bricks,  and  these  should 
be  laid  out  before  the  frame  of  the  table  is  made,  so  as  to  get  the 
correct  size  for  the  bricks  to  fit  well  together. 

Fig.  53  is  an  adjustable  type  and  can  be  turned  at  any  angle. 
This  is  found  exceptionally  useful  on  repairs,  when  the  welding 
is  not  horizontal.  One  has  a  vice  attachment,  and  is  very  useful. 

In  large  shops,  where  there  are  a  large  number  of  operators  on 
repetition  work,  it  is  a  practice  to  construct  long  tables  at  which 
thirty  to  forty  operators  can  all  work.  They  usually  work  face  to 


102  MODERN  METHODS  OF  WELDING 


FIG.  54. — WELDING  TABLE  WITH  FIRE-BRICKS. 


O        MAIN  FROM  GENERATOR 


r 


H 


FIG.  55. — TABLE  FOR  A  NUMBER  or  OPERATORS. 


WELDING  TABLES 


103 


face — that  is,  in  pairs  each  side  of  the  table.  The  acetylene  main 
gas  pipe  is  usually  brought  over  the  centre  of  the  table,  and  the 
hydraulic  safety  valves  are  suspended  from  the  main  supply  to  a 
convenient  position  for  the  operators.  They  are  spaced  according 
to  the  requirements  of  the  articles  being  welded  without  crowding. 


FIG.  56.— TILTING  TABLE. 
Articles  can  be  bolted  on. 

In  construction,  these  tables  are  almost  identical  with  the  smaller 
ones,  with  the  exception  that  no  frames  are  used,  except  the  framing 
under  the  boiler-plate  top.  Such  large  tables  usually  have  large 
flat  bricks,  about  1J  inches  thick.  Fig.  55  is  a  sketch  of  one, 
showing  the  position  of  the  acetylene  main  gas-supply,  from  which 
are  suspended  the  hydraulic  safety  valves,  one  for  each  operator. 
The  tables  may  be  extended  to  any  length,  to  the  limit  of  the  shop 
and  the  supply  of  acetylene. 


CHAPTER  XIX 
FURNACES  FOR  HEATING 

IN  the  repair  of  non-ductiles,  it  is  necessary  to  heat  them  up  before 
the  welding  can  take  place.  It  is  impossible  to  make  satisfactory 
welds  of  cast-iron  or  aluminium  articles  without  first  preheating  to 
a  level  temperature.  If  an  attempt  is  made  to  weld  any  articles  of 
the  metals  stated  above,  without  getting  hot  all  over,  fractures  take 
place.  For  instance,  take  a  casting  of  iron  just  as  it  is,  without 
preheating.  Apply  the  blowpipe  at  any  place,  get  a  good  heat, 
and  the  result  is  that  you  will  hear  it  crack  in  some  part  other  than 
where  heated.  When  the  casting  gets  cold  again,  further  fractures 
are  sure  to  occur.  These  are  caused  by  the  uneven  heating  of  the 


JOL- 


FIG.  57. — KEROSENE  PREHEATING  TORCH. 

article  in  one  place  with  the  blowpipe,  causing  the  non-conducting 
metal  to  expand  where  it  was  hot,  while  the  cold  part  of  the  casting 
remained  normal. 

The  methods  adopted  to  overcome  this  expansion  and  contrac- 
tion on  non-ductile  articles  are  very  simple,  if  care  is  taken  to  pro- 
vide the  right  appliances.  One  is  to  use  a  furnace  with  coal,  coke, 
charcoal,  or  gas.  Coal  would  be  all  right  in  a  properly  constructed 
furnace,  where  the  flame  is  reverberatory,  and  a  second  floor  has 
been  made  for  the  heating  of  the  articles  which  are  not  in  actual 
contact  with  the  fire.  But  the  author's  experience  is  that  this 
method  is  much  too  costly  to  maintain.  The  expense  would  be 

104 


FURNACES  FOR  HEATING 


105 


prohibitive  in  a  small  shop,  unless  there  was  a  good  quantity  of 
castings  to  weld  daily.  Also  the  heat  is  too  fierce,  and  would  not 
do  at  all  for  aluminium,  which  would  probably  collapse  before 
it  could  be  got  out.  The  coal  furnace  should  only  be  used  in  large 
shops.  Although  there  are  many  of  these  furnaces  being  used, 
with  coal,  coke,  and  charcoal,  and,  to  a  certain  degree,  giving 


FIG.  58. — GAS-HEATED  PREHEATING  OVEN. 


satisfaction,  they  are  generally  employed  in  conjunction  with  other 
work.  The  best  method,  with  the  least  initial  outlay,  the  most 
economical  working,  and  the  best  even  heating,  is  a  furnace  heated 
by  gas  at  either  ordinary  or  high  pressure.  Fig.  58  shows  an 
excellent  type,  which  gives  exceptionally  good  results;  it  is  not 
hard  to  make,  and  it  will  not  be  expensive. 

Fig.  57  shows  a  preheating  kerosene  torch.     This  is  ideal  for 


106 


MODERN  METHODS  OF  WELDING 


the  repair  shop;  it  is  light,  portable,  and  owing  to  a  patented 
sliding  valve,  can  be  operated  in  any  position.  It  produces  a 
clean  even  flame  of  about  3,000°  F.  and  24  inches  long.  It  con- 
sumes about  1  gallon  of  kerosene  per  hour.  The  tank  capacity 
is  3  gallons.  The  burner  thoroughly  vaporises  the  kerosene,  and 
the  flame  cannot  blow  out  in  the  wind.  It  is  very  good  for  pre- 
heating work  and  also  for  annealing.  The  weight  is  25  pounds. 

The  preheating  oven  or  furnace  shown  on  p.  105  is  easy  to  con- 
struct from  sheet  steel.  It  was  designed  by  the  author,  and  has 
proved  very  efficient  in  use.  It  may  be  made  any  size  to  suit  the 
work  in  hand.  The  one  illustrated  is  4  feet  deep,  3J  feet  wide,  3  feet 
long.  The  construction  consists  of  an  inner  and  outer  casing,  with 


J L 


J L 


1 LbJ I 


FIG.  59. — FOLDING  ASBESTOS  SCREEN,  FOR  PREHEATING  FURNACE. 

1J  inches  space  between  them,  filled  with  asbestos.  The  back  of 
the  stove  (inner  and  outer)  must  have  the  asbestos  put  between 
before  bolting  up  the  stove.  There  is  an  outlet  at  the  back,  near 
the  top,  to  allow  the  burnt  gases  to  escape,  and  the  piping  should  be 
carried  from  the  outlet  to  the  atmosphere.  On  the  inside  of  the 
stove  are  bearers  or  ledges  for  perforated  trays,  in  which  trays  the 
articles  for  heating  are  fixed.  The  door  is  also  made  of  two  sheets 
of  steel,  with  asbestos  between  them,  and  fits  very  closely  to  prevent 
any  cold  air  from  getting  into  the  interior.  Along  the  bottom  are 
four  Bunsen  burners.  These  may  be  purchased  from  any  reliable 
firm,  but  they  must  be  the  best  that  can  be  got. 

A  great  saving  in  gas  can  be  made  by  adopting,  for  the  purpose 
of  extracting  all  the  heat  from  gas,  a  folding  asbestos  cover  as  in 
Fig.  59.  It  is  made  like  a  fourfold  screen.  After  the  article  to  be 


FURNACES  FOR  HEATING 


107 


heated  is  put  in  the  stove,  and  before  the  gases  are  lit,  it  is  placed 
on  the  top  of  the  article.  When  the  gases  are  lit,  this  cover  concen- 
trates the  whole  of  the  heat,  thereby  getting  the  article  heated  in  a 
much  shorter  time,  and  saving  quite  50  per  cent,  of  the  gas.  This 
asbestos  cover  can  be  used  for  preheating  and  also  for  annealing. 
The  screen  described  may  be  made  in  smaller  or  larger  sizes  to  suit 
the  work  required.  The  perforated  tray  in  the  furnace  is  made  to 
draw  out  with  the  article  on  it. 

The  handling  of  castings,  such  as  a  four-cylinder  motor  casting, 
when  hot,  is  a  very  troublesome  job  if  there  are  no  proper  appliances. 
Hence,  fractures  often  occur  through  not  getting  the  articles  quickly 
enough  into  the  annealing  furnace,  and  allowing  the  temperature 
to  fall  into  the  expansion  zone — that  is,  850°  C.  The  author  has 


FIG.  60. — LIGHT  LIFTING  CRANE  FOR  USE  IN  LIFTING  CASTINGS  IN  AND  OUT 
OF  THE  PREHEATING  FURNACE. 


known  this  to  occur  on  many  occasions.  Good  welds  have  been 
executed,  but  they  have  been  left  one  or  two  minutes  too  long  before 
getting  them  into  the  annealing  furnace,  and  very  often  the  fracture 
is  much  larger  than  the  original  fracture.  An  appliance  which,  will 
be  found  to  overcome  this  difficulty  of  removing  and  inserting  the 
hot  articles  rapidly,  with  ease  and  comfort,  is  shown  in  Fig.  60. 
This  should  be  installed  in  all  workshops  where  they  are  dealing 
with  heavy  repairs,  which  have  to  be  preheated.  It  is  simply  a 
small  swinging  overhead  crane,  very  lightly  built,  to  carry  about 
5  cwt.  It  has  two  small  wheels,  running  along  a  flat  bar  on  edge. 
Suspended  from  the  plates  of  the  wheels  is  a  lever  about  9  feet 
long,  a  hook  on  the  end,  and  a  rope  at  the  other. 

The  rope  is  for  lifting  the  weight  suspended  at  the  other  end ;  on 
the  hook  may  be  hung  a  two-  or  four-legged  chain  to  lift  the  articles 


10S  MODERN  METHODS  OF  WELD1> 

already  fixed  on  the  oven  tray.  The  hot  casting  may  thus  be  pat 
in  and  out  of  the  oven  or  furnace  with  ease,  and  without  any  of  the 
welders  getting  burnt. 

The  phenomenon  of  expansion  and  contraction  with  reference 
to  metals  is  one  of  the  most  important  problems  in  the  welding  pro- 
cess -  N  operator  can  become  competent  without  devoting  long 
study  to  it.  Cast  iron  is  a  non-ductile  metal — that  is,  it  can  only 
expand  and  contract  in  its  whole  piece.  Hence,  if  heat  is  applied  to 
one  part  of  the  article,  the  heated  part  becomes  expanded  pas 
elastic  limit.  The  cold  part  of  the  article  does  not  expand  and  the 
heated  part  is  therefore  fractured.  On  the  other  hand,  if  the  whole 
article  had  been  heated,  by  putting  in  a  proper  heating  furnace, 
and  the  heat  carefully  regulated  until  it  had  reached  a  minimum  of 
900  C.3  the  article  could  have  then  been  taken  from  the  furnace  and 
put  on  the  welding  table,  welded,  and  put  back  into  the  annealing 
furnace  and  allowed  to  cool  slowly,  preventing  any  cold  air  from 
getting  near  it,  when  the  article  would  be  quite  sound  without 
crack  or  fracture. 

This  operation  of  expansion  and  contraction  is  so  important,  and 
the  methods  to  counteract  it  are  so  easy,  sure,  and  effee: 
t  ha  t .  in  all  cases  where  welding  of  non-ductile  articles  is  done,  one 
must  see  to  it  that  these  operations  of  preheating  and  annealing  are 
carried  out. 


CHAPTER  XX 
IRON  AND  STEEL 

mechanical  properties  of  metals  are  often,  in  a  great  measure, 
dependent  on  the  thermal  treatment  to  which  they  have  been  sub- 
jeeted.  There  ran  be  no  question  that  the  application  of  heat  to  a 
metal  may  produce  a  remarkable  molecular  change  in  its  structure, 
the  nature  of  the  change  depending  on  that  of  the  metal,  and  on  the 
treatment  it  has  undergone.  It  will  be  well,  therefore,  to  consider 
fully  what  happens  when  the  metals  are  submitted  to  three 
principal  operations  involving  thermal  treatment,  which  are  known 
respectively  as  annealing,  hardening,  and  tempering.  Usually  all 
three  are  intimately  related.  Annealing  may  be  defined  as  the 
release  of  the  strain  in  metals,  \\hich  may  itself  have  been  produced 
by  mechanical  treatment,  such  as  hammering,  rolling,  or  wire- 
drawing, or  by  either  rapid  or  slow  cooling  from  a  more  or  less 
elevated  temperature. 

n  example  of  the  former,  it  may  be  mentioned  that  metals  and 
alloys  which  have  been  rendered  excessively  hard  by  rolling  are 
heated  usually  to  bright  redness  and  allowed  to  cool  slowly.  In  the 
case  of  copper  it  does  not  appear  to  be  important  whether  the  cooling 
nv  or  rapid,  and  in  recent  years  much  experimental  evidence 
has  been  accumulated  which  tends  to  show  that,  in  the  case  of  certain 
metals  which  have  been  hardened,  a  more  en-  less  prolonged  exposure 
to  a  low  temperature  under  100''  r.  will  sensibly  anneal  them. 
On  the  other  hand,  the  rapidity  with  which  cooling  is  etTected  is  very 
important.  l>ron/.e  containing  about  20  per  cent,  of  tin  is  rendered 
very  malleable  by  rapid  cooling.  In  the  ease  of  iron  and  steel  the 
thermal  treatment  is  especially  important. 

Steel,  it  must  be  remembered,  is  modified  iron.  The  name  iron 
is.  in  fact,  a  comprehensive  one.  for  the  mechanical  behaviour  of 
the  metal  is  so  singularly  changed  by  influences  acting  from  within 
and  without  its  mass  as  to  lead  many  to  think  that  iron  and  steel 
must  be  two  distinct  metals:  their  properties  are  so  different. 
Pure  iron  may  be  prepared  in  a  form  as  pliable  and  soft  as  copper 
— for  instance,  the  charcoal  used  for  welding.  Steel  can  readily  be 
made  sutHciently  hard  to  scratch  glass.  Notwithstanding  this  cxtra- 

109 


110  MODERN  METHODS  OF  WELDING 

ordinary  variation  in  the  physical  properties  of  iron  and  certain  kinds 
of  steel,  the  chemical  difference  between  them  is  small,  and  would 
hardly  secure  attention  if  it  were  not  for  the  importance  of  the 
results  to  which  it  gives  rise. 

It  is  necessary  to  consider  the  nature  of  the  transformations 
which  iron  can  sustain,  and  to  see  how  it  differs  from  steel.  Its  most 
useful  and  advantageous  property  is  that  of  becoming  extremely 
hard  when  ignited  and  plunged  in  cold  water,  the  hardness  produced 
being  greater  in  proportion  as  the  steel  is  hotter  and  the  water  colder. 
The  colours  which  appear  on  the  surface  of  steel  slowly  heated 
direct  the  artist  in  tempering  or  reducing  the  hardness  of  steel  to 
any  determinate  standard. 

Hardening  is  the  result  of  rapidly  cooling  a  strongly  heated  mass 
of  steel. 

Tempering  consists  of  reheating  the  hardened  steel  to  a  tempera- 
ture far  short  of  that  to  which  it  was  raised  before  hardened.  This 
heating  may  or  may  not  be  followed  by  rapid  cooling. 

Annealing,  as  applied  to  steel,  consists  in  heating  the  mass  to  a 
temperature  higher  than  that  used  for  tempering,  and  allowing  it  to 
cool  slowly. 

This  may  be  seen  experimentally  in  the  following  manner :  Three 
strips  of  steel  of  identical  quality  may  be  taken.  It  can  be  shown 
by  bending  one  that  it  is  soft,  but  if  it  is  heated  to  redness  and 
plunged  in  cold  water  it  will  become  hard  and  will  break  on  any 
attempt  to  bend  it.  The  second  strip  may,  after  heating  and  rapid 
cooling,  be  again  heated  to  about  the  melting-point  of  lead,  \\hen  it 
will  bend  readily,  and  will  spring  back  to  a  straight  line  when  the 
bending  force  is  removed.  The  third  piece  may  be  softened  by  being 
cooled  slowly  from  a  bright-red  heat.  This  will  bend  easily  and 
will  remain  distorted. 

The  metal  has  been  singularly  altered  in  its  properties  by  com- 
paratively simple  treatment.  And  all  these  changes,  it  must  be 
remembered,  have  been  produced  in  a  solid  metal,  to  which  nothing 
has  been  added,  and  from  which  no  material  has  been  taken  away. 
The  theory  of  the  operation  described  above  has  been  laboriously 
built  up ;  its  consideration  introduces  many  questions  of  great  interest 
both  in  the  history  of  science  and  our  knowledge  of  molecular  physics. 

Physical  Properties  of  Metals. 

Molecular  Structure. — The  physical  aspects  of  metal  are  so  pro- 
nounced as  to  render  it  difficult  to  abandon  the  old  view  that  metals 
are  sharply  denned  from  other  elements,  and  form  a  class  by  them- 


IRON  AND  STEEL  111 

selves.  Like  all  other  elements,  metals  are  composed  of  atoms 
grouped  in  molecules.  Any  force  that  alters  the  relations  of  the 
atoms  in  molecules  modifies  the  physical  properties  of  the  metals. 
Indeed,  it  would  be  easy  to  show  that  the  physical  constants  of  each 
metal  vary  with  its  degree  of  purity.  The  molecular  grouping  of 
metals  is  doubtless  very  varied,  and  little  definite  is  known 
regarding  the  structural  stability  of  most  of  them;  but  it  may  be 
assumed  that  it  is  not  very  great,  as  some  metals  split  up  into  single 
atoms  when  they  are  volatilised,  and  most  of  them  unite  readily 
with  chlorine  and  oxygen.  Consequently,  any  mass  of  which  the 
fundamental  molecules  are  the  constituent  particles  may  practically 
be  regarded  as  a  single  molecule.  Two  fundamental  molecules  must, 
however,  be  held  to  be  capable  of  uniting  to  form  complexes  that 
have  less  power  of  cohering,  and  any  circumstances  tending  to  bring 
about  the  formation  of  such  complexes  would  tend  to  make  the 
material  less  tough.  This  may  account  for  the  extraordinary  altera- 
tion in  the  properties  of  many  metals  produced  by  very  small  quan- 
tities of  incompatible  foreign  matters. 

Density. — The  density  of  the  metal  is  dependent  on  the  intimacy 
of  the  contact  between  the  molecules.  It  is  dependent,  therefore, 
on  the  crystalline  structure,  and  is  influenced  by  the  temperature 
of  the  casting,  by  the  rate  of  cooling,  by  mechanical  treatment,  by 
the  purity  of  the  metal.  All  metals,  except  bismuth,  are  lighter 
when  molten  than  in  the  solid  state.  In  the  case  of  cast  iron,  which 
passes  through  a  pasty  state  on  solidification,  the  density  is  aug- 
mented by  wire-drawing,  hammering,  and  any  other  physical  method 
of  treatment  in  which  a  compressing  stress  is  employed.  Mere 
traction,  however,  may  diminish  the  density  by  tending  to  develop 
cavities  in  the  metal.  Pressure  on  all  sides  of  a  piece  of  metal 
increases  its  density.  A  metal  can  only  be  compressed  if  the 
result  of  the  application  of  pressure  is  to  cause  it  to  pass  to  an 
allotropic  state — that  is,  denser  than  that  which  it  originally 
possessed. 

Fracture. — The  appearance  of  the  fractured  surface  of  a  metal 
depends  partly  on  the  nature  of  the  metal  and  partly  on  the  manner 
in  which  solidification  occurred.  Sudden  cooling,  to  a  great  extent, 
prevents  the  formation  of  crystals,  while  slow  cooling  facilitates 
their  development.  Long,  continual  hammering,  frequent  vibra- 
tions, and  intense  cold  will  produce  the  latter  result.  Any  condition 
that  affects  either  the  cohesion  or  the  crystalline  structure  of  a  metal 
affects  its  fracture. 

Malleability. — -This  is  a  property  of  permanently  extending  in 


112  MODERN  METHODS  OF  WELDING 

all  directions,  without  rupture,  through  pressure  produced  by  slow 
stress  or  by  impact.  As  a  rule,  crystalline  metals  are  not  malleable, 
and  any  circumstances  that  tend  to  produce  crystallisation  must 
affect  the  malleability.  Thus,  in  nearly  all  metals,  the  malleability 
becomes  impaired  when  they  are  subjected  to  rolling  or  long-con- 
tinued hammering.  But  this  property  may  be  regained  by  anneal- 
ing, which  consists  in  raising  the  metal  to  a  high  temperature  and 
allowing  to  cool,  either  rapidly  or  slowly.  At  different  temperatures 
metals  behave  in  different  ways. 

Every  malleable  compound  of  iron,  containing  the  ordinary 
elements  of  that  metal,  which  is  obtained  either  by  the  union  of  pasty 
masses  of  the  iron  or  by  any  process  involving  fusion,  and  which 
cannot  be  hardened  by  an  ordinary  method,  will  be  called  by  us 
"  wrought  iron." 

Ductility  is  the  property  which  enables  metals  to  be  drawn  into 
wire.  It  generally  decreases  with  an  increase  in  temperature  of 
the  wire  at  the  time  of  drawing ;  but  there  is  no  regular  ratio  between 
the  two.  Iron  is  less  ductile  at  100°  C.  and  more  ductile  at  200°  C. 
than  it  is  at  0°  C. 

Tenacity  is  the  property  possessed  by  metals,  in  varying  degrees, 
of  resisting  the  separation  of  their  molecules  by  the  action  of  a  tensile 
stress. 

Toughness  is  the  property  of  resisting  the  separation  of  the  mole- 
cules after  the  limit  of  elasticity  has  been  passed. 

Hardness  is  the  resistance  offered  by  the  molecules  of  a  substance 
to  their  separation  by  the  penetrating  action  of  another  substance. 
Great  differences  are  observable  between  the  hardness  of  various 
metals. 

Elasticity  is  the  power  a  body  possesses  of  resuming  its  original 
form  after  the  removal  of  an  external  force  which  has  produced  a 
change  in  that  form.  The  point  at  which  the  elasticity  and  the 
applied  stress  exactly  counterbalance  each  other  is  termed  the 
"  limit  of  elasticity."  If  the  applied  stress  were  then  removed,  the 
material  acted  upon  would  resume  its  original  form.  If,  however, 
the  stress  were  increased  the  change  in  form  would  become  per- 
manent, and  permanent  set  would  be  effected.  Within  the  limit 
of  elasticity,  a  uniform  rod  of  metal  lengthens  or  shortens  equally 
under  equal  additions  of  stress.  If  this  were  the  case  beyond  that 
limit  it  is  obvious  that  this  would  stretch  the  bar  to  twice  its  original 
length,  or  shorten  it  to  zero.  This  stress,  expressed  in  pounds  or 
tons  for  a  bar  of  1-inch  square  cross-section,  is  termed  the  modulus 
of  elasticity. 


IRON  AND  STEEL  113 

The  ultimate  tensile  strength  or  maximum  stress  the  material 
can  sustain  without  rupture,  the  limit  of  elasticity,  and  the  breaking 
stress  are  the  points  which  usually  have  to  be  determined,  and  these 
alone  will  be  considered  here.  In  testing  a  piece  of  metal,  the  first 
point  to  be  determined  is  the  limit  of  elasticity.  When  a  metal, 
such  as  a  piece  of  iron  or  steel,  is  submitted  to  stress  by  pulling  its 
ends  in  opposite  directions,  it  stretches  uniformly  throughout  its 
length.  There  is,  however,  in  such  a  solid  a  limit  in  the  applica- 
tion of  the  stress  up  to  which  the  metal,  if  released,  will  return  to 
its  normal  length.  This  point  is  the  limit  of  elasticity. 

Influence  of  Foreign  Elements  on  the  Strength  of  Metals. — The 
influence  of  chemical  compositions  on  the  mechanical  properties 
of  metals  is  of  great  importance.  The  influence  of  foreign  elements 
is  best  shown  in  the  case  of  iron.  The  properties  of  this  metal  are 
absolutely  changed  by  the  presence  of  a  few  tenths  per  cent,  of 
carbon.  Phosphorus  and  silicon  produce  very  dangerous  impurities 
in  iron.  It  is  difficult  to  estimate  the  influence  of  silicon.  It  is 
known  that  its  addition  to  molten  steel  is  useful,  as  it  prevents  the 
formation  of  blowholes  in  the  solidifying  mass. 

The  colour  of  metals  is  influenced  by  their  purity.  Thus,  iron 
becomes  white  by  the  admixture  of  carbon,  silicon,  sulphur,  and 
phosphorus.  All  metals  are  fusible.  When  strongly  heated,  they 
pass  from  a  brownish-red  to  a  clear  red  colour,  which  gradually 
increases  in  luminosity  and  transparency  to  a  dazzling  white.  On 
solidifying  from  a  molten  state,  metals  frequently  exhibit  efferves- 
cences due  to  the  expulsion  of  absorbed  gases.  This  expulsion,  before 
solidification,  causes  a  sudden  outburst  of  metal  through  the  surface. 
When  it  passes  from  the  liquid  to  the  solid  state,  it  either  does  so 
suddenly,  or  it  passes  through  an  intermediate  pasty  stage.  This 
fact  is  occasionally  of  great  metallurgical  importance. 

On  solidification  after  melting,  metals  usually  crystallise. 
The  crystallisation  of  metals  is  of  great  importance,  as  the  formation 
of  crystals,  due  to  continued  vibration,  intense  cold,  sudden  altera- 
tions of  temperature,  or  the  presence  of  impurities,  may  render  a 
metal  absolutely  useless.  Welding  is  the  property,  possessed  by 
metals  which,  on  cooling  from  the  molten  state,  pass  through  a 
plastic  stage  before  becoming  perfectly  solid,  of  being  joined  together 
by  the  cohesion  of  the  molecules  introduced  by  the  application  of  an 
extraneous  force,  such  as  hammering.  This  property  is  exhibited 
in  a  marked  degree  by  iron  and  platinum  at  a  white  heat. 

All  steel  is  iron,  differing  only  in  containing  a  larger  percentage 
of  carbon,  usually  with  a  small  quantity  of  silicon  and  manganese, 


114  MODERN  METHODS  OF  WELDING 

and  often  a  small  percentage  of  some  other  metal.  What  is  known 
as  mild  steel  is  a  product  that  stands  between  wrought  iron  and  the 
hardest  steel,  as  that  used  for  making  cutting  tools.  This  mild 
steel  has  largely  taken  the  place  of  wrought  iron  and  is  used  in  the 
construction  of  steel  buildings.  Pure  iron  is  a  soft,  greyish-white 
metal,  very  ductile  and  malleable,  and  highly  tenacious.  This  is 
generally  used  as  welding  iron.  After  fusion,  pure  iron  exhibits 
a  crystalline  scaly  fracture.  It  is  softer  than  wrought  iron,  and  is 
not  affected  by  heating  to  redness  and  quenching  in  cold  water. 
It  is  highly  magnetic,  and  welds  readily.  Its  specific  heat  is  0-113 
and  its  specific  gravity  7-675.  It  melts  to  a  lower  temperature  than 
platinum,  about  1,600°  C.  In  mass  it  is  unaffected  by  dry  or  moist 
air,  and  more  so  in  oxygen,  yielding  a  scaly  coating  of  oxide.  When 
molten,  it  dissolves  or  occludes  various  gases  in  considerable  quan- 
tities. Hydrogen,  carbon  monoxide,  and  nitrogen  are  thus  taken 
up  and  given  out  on  cooling. 

The  above  physical  properties  are  present  in  a  greater  or  less 
degree  in  cast  or  wrought  iron  and  steel,  the  extent  to  which  they  are 
modified  depending  on  the  purity  of  the  substance.  These  bodies 
consist  of  iron  containing  varying  proportions  of  carbon,  silicon, 
manganese,  sulphur,  phosphorus,  etc.  The  main  difference  between 
the  properties  of  cast  and  wrought  iron  and  steel  are  due  to  the 
presence  of  carbon  in  the  metal,  depending  on  the  amount  and  the 
manner  in  which  it  exists  in  the  iron.  The  maximum  amount  of 
carbon  taken  up  by  pure  iron  is  stated  to  be  0-475  per  cent.  In 
cast  iron  containing  manganese,  a  little  over  5  per  cent,  may  be 
present.  Steel  may  contain  up  to  1-8  per  cent.,  while  the  carbon  in 
wrought  iron  seldom  exceeds  0-25  per  cent,  and  may  fall  as  low  as 
0-05  per  cent. 

The  designation  of  steel  was  formerly  confined  to  those  varieties 
of  iron  which  could  be  hardened  by  heating  to  redness  and  plung- 
ing in  cold  water.  The  introduction  of  the  Bessemer  process  marked 
a  new  era.  The  metal  produced  by  that  process  lacks  the  fibrous 
character  associated  with  wrought  iron  and  partakes  more  or  less 
of  the  character  of  steel.  Varieties  possessing  more  than  0-3  per 
cent,  of  carbon  sensibly  harden  when  treated  in  the  same  manner 
as  steel.  Some  steels  are  even  softer  than  wrought  iron.  Since  the 
hardening  property  is  dependent  on  the  amount  of  carbon  contained, 
a  classification  based  on  the  percentage  of  that  element  is  most 
convenient.  Steel  containing  less  than  0-5  per  cent,  is  classed  as  mild 
steel.  The  different  nature  of  the  metals  may  be  shown  by  the  use 
of  such  titles  as  Bessemer,  Siemens,  or  open-hearth  steel.  Some 


IRON  AND  STEEL  115 

of  these  contain  as  little  as  0-08  per  cent,  of  carbon — less  than  is  of  ten 
present  in  wrought  iron.  (This  is  the  easiest  of  all  steels  to  weld, 
but  very  little  of  it  is  manufactured,  not  being  the  usual  standard.) 
They  differ  from  wrought  iron  in  being  devoid  of  fibre,  more  homo- 
geneous, and,  unlike  it,  are  obtained  in  a  state  of  fusion. 

The  fracture  of  steel  becomes  finer  the  larger  proportion  of 
carbon  present,  but  it  is  affected  by  such  treatment  as  hammering. 

Cold  steel  of  hard  temper  breaks  with  a  clear,  uniform,  grey, 
fine,  granular  fracture.  After  hardening,  the  colour  is  somewhat 
whiter.  It  is  very  malleable,  but  requires  working  more  carefully 
and  at  a  lower  temperature  than  wrought  iron.  Steel  containing 
less  than  1-25  per  cent,  of  carbon  can  be  welded,  but  at  a  lower 
temperature  than  wrought  iron,  or  the  steel  will  be  burnt.  To 
render  the  surfaces  clean  at  the  lower  heat,  borax  mixed  with 
one-tenth  of  its  weight  of  sal  ammoniac  should  be  employed  to 
dissolve  the  scale. 

The  specific  gravity  of  steel  varies  from  7-624  to  7-813.  The 
melting-point  varies  with  the  proportion  of  carbon.  The  softest 
melts  a  little  below  1,600°  C.  The  tenacity  varies  from  22  tons  in 
mild  steel  to  70  tons  in  steel  of  hard  temper.  The  elasticity  exceeds 
that  of  wrought  iron,  while  the  ductility  is  equal  to  the  best  qualities 
of  that  substance.  The  mild  varieties  suffer  an  elongation  and 
diminution  in  area  when  subject  to  a  stretching  force  greater  than 
wrought  iron.  The  elongation  of  the  harder  varieties  is  much  less, 
but  the  elastic  limit  is  high.  Mild  steels,  when  being  welded  and 
becoming  molten  at  the  weld,  are  liable  to  "  bod."  This  is  due  to  the 
disengagement  of  dissolved  gases,  mainly  H,  N,  and  CO,  which  are 
given  up  as  the  metal  cools  off.  The  bubbles  of  the  gas  cause  the 
metal  to  be  honeycombed  and  vascular. 

Tenacity  of  metal  is  determined  by  straining  a  piece  of  metal 
of  known  dimensions,  and  observing  the  amount  of  force  necessary 
to  fracture  it.  Elongation,  the  extent  to  which  a  metal  elongates 
prior  to  fracture,  is  a  matter  of  greatest  importance.  Tough  ductile 
metals  show  a  considerable  increase  in  length ;  hard,  brittle  metals 
elongate  but  little.  Important  evidence  as  to  the  working  qualities 
of  the  material  and  efficiency  of  the  weld  is  furnished.  To  deter- 
mine the  elongation,  the  test-piece  is  measured  between  the  points 
at  which  it  is  gripped  before  and  after  straining  till  fractured  (it  is 
usual  to  put  two  marks  on  the  test-piece  for  ^measuring),  and  the 
increase  is  stated  in  percentage  of  the  original  length.  Thus  a 
10-inch  test-piece  of  boiler  steel  measured  12-5  inches  after  fracture 
— i.e.,  2-5  inches  over  10  inches,  or  25  per  cent.  Elongation  is 


116  MODERN  METHODS  OF  WELDING 

accompanied  by  a  diminution  in  area  of  section.  This  is  measured 
in  order  to  determine  whether  the  elongation  was  local  or  uniformly 
distributed.  Sometimes  the  contraction  in  area  is  confined  to  the 
region  of  the  fracture. 

Some  Difficulties  in  Welding. 

Welds  on  mild  steel,  which  apparently  are  the  most  easy  to 
obtain,  are  in  reality  those  which  require  the  greatest  study  and 
skill  on  the  part  of  the  operator.  The  welding  must  be  done  to  give 
the  weld  the  mechanical  properties  approaching  those  of  the  metal 
to  be  welded.  In  cases  where  the  process  is  applied  without  the 
knowledge  of  the  technique,  the  strength  of  the  metal  and,  above 
all,  its  elongation  are  considerably  lowered.  In  short,  the  operation 
of  welding  can  lower,  at  the  line  of  joining,  the  principal  qualities  of 
mild  steel,  which  are  particularly  required  in  metallic  construction. 

If  the  operator  will  go  thoroughly  through  the  chapter  on  iron  and 
steel,  he  will  learn  much  that  will  be  of  great  assistance  to  him  in 
his  welding.  One  of  the  important  things  to  remember  in  welding 
iron  and  steel  is  the  formation  of  the  oxide  and  its  inclusion  in  the 
metal  forming  blowholes.  It  is  to  be  noted  that  there  is  always 
a  formation  of  oxide  at  the  surface  of  the  iron  and  steel  melted  under 
the  action  of  the  blowpipe.  This  oxide  fuses  before  the  metal,  and 
is  lighter.  Therefore  it  rises  to  the  surface  of  the  metal  when  molten, 
and  can  be  eliminated  by  passing  the  welding-rod  in  a  horizontal 
position  over  the  weld  while  the  metal  is  molten.  Steel  and  iron 
in  a  molten  state  dissolve  !•!  per  cent,  of  oxide.  This  is  always  the 
case,  and  unless  the  operator  has  full  knowledge  of  the  technical 
and  metallurgical  points,  he  prevents  the  joints  standing  the  stresses 
required.  The  technique  of  oxy-acetylene  welding  is  very  little 
known,  and  there  are  yet  many  problems  to  be  discovered. 

Many  operators  make  the  frequent  mistake  of  interposing 
oxide  in  the»weld.  In  nearly  all  these  cases  this  is  caused  by  burn- 
ing of  the  weld,  when  an  excess  of  oxygen  is  used,  the  flame  held 
on  the  weld  too  long,  and  too  large  a  surface  liquid.  It  causes  the 
weld  to  become  "  cinderised."  In  the  melting  period  of  the  weld  the 
suspended  particles  are  no  doubt  due  to  the  spitting  of  the  metal  as  it 
fuses,  but  the  origin  of  the  oxide  when  the  molten  metal  is  covered 
with  the  slag  is  less  certain.  It  may  possibly  be  due  to  the  presence 
of  iron  vapour  in  numerous  bubbles  of  carbon  monoxide  formed 
throughout  the  molten  weld;  or  probably  to  the  spurting  of  the 
molten  metal.  The  oxide  defuses  in  the  molten  metal,  and  reaction 
takes  place  with  the  carbon  and  manganese  and  reduces  their 


IRON  AND  STEEL 


117 


strength.  The  dissolving  of  the  gases  may  be  given  up,  if  the 
operators  take  care,  when  the  metal  is  molten,  to  allow  these  gases 
to  escape,  and  to  make  good  solid  welds. 

One  fault,  of  which  many  operators  are  guilty,  is  to  use  a  too 
high-powered  blowpipe,  or  to  use  too  high  pressure  of  oxygen,  which 
causes  an  over-fierce  flame.  Consequently  the  metal  has  not  time 
to  get  thoroughly  hot  before  it  begins  to  become  liquid.  Only 
just  the  surface  is  "swilled,"  and  the  underneath  layer  is  not 
anywhere  near  the  welding-point.  This  is  the  cause  of  many  defec- 
tive welds  in  which  there  is  adhesion  and  oxide  is  interposed  in  the 
weld. 


I   r^  I 


FIG.  61.— TENSION AL  TESTS,  WELDED  FLAT  AND  BARS. 

This  can  be  avoided  if  the  proper-sized  blowpipe  is  used,  and  the 
pressure  of  oxygen  is  that  prescribed  by  the  makers  of  the  blowpipe, 
and  no  more.  Then  the  weld  must  be  proceeded  with  at  a  moderate 
speed,  giving  time  for  the  edges  of  the  article  to  melt  thoroughly 
into  a  thick  liquid  form.  Then  the  feeding-rod  must  be  added  and 
the  weld  filled  up.  The  blowpipe  must  not  be  allowed  to  remain  on 
the  metal  after  it  has  been  melted  (and  the  tip  must  be  kept  about 
•f V  inch  from  the  metal  that  is  being  welded)  as  it  burns  the  metal 
after  the  first  melting.  If  the  metal  gets  too  hot,  it  becomes  too 
liquid  and  is  burnt,  and  the  carbon  and  other  elements  are  partly 
destroyed,  thereby  reducing  the  strength  of  the  weld  considerably. 


118  MODERN  METHODS  OF  WELDING 

The  point  of  the  molten  metal  should  be  just  a  thick  liquid,  and 
should  never  be  made  hotter  or  thinner  liquid,  which  causes  oxida- 
tion and  swilling. 

The  author  would  draw  attention  again  to  his  previous  remarks 
as  to  operators  testing  their  work  from  time  to  time.  Leading 
engineers,  through  so  many  past  failures,  and  so  many  bad  and 
defective  welds,  are  not  very  favourable  to  allowing  oxy-acetylene 
welding  to  be  done  on  anything  that  has  to  stand  any  great  stresses. 
Therefore  operators  should,  without  fail,  make  repeated  tests  from 
sample  welded  joints,  as  outlined  in  previous  chapters.  In  addition 
to  the  tests  explained,  tensional,  distortional,  and  other  mechanical 
tests  can  be  made,  and  will  greatly  assist  operators  in  becoming 
efficient.  These  latter  tests  many  schools  would  be  glad  to  make 
on  their  behalf. 

Blowpipes  must  be  the  best,  if  good  welding  is  required.  The 
previous  chapter  on  the  subject  has  laid  this  down;  a  further 
paragraph  will  help  to  emphasise  their  importance.  Absolutely 
the  best  blowpipe  must  be  procured,  irrespective  of  cost.  In  the 
selection  the  following  points  should  be  considered :  The  blowpipe 
must  have  a  constant  clear  flame  with  a  distinct  white  cone,  as  large 
as  possible  and  sharp-edged;  must  be  easy  of  regulation;  must  not 
back-fire.  There  must  be  a  proper  mixture  of  the  gases  at  the  nozzle 
outlet,  and  at  the  correct  pressure  specified  by  makers,  and  no  more. 
There  must  be  no  excess  of  acetylene  (which  carbonises),  no  excess 
of  oxygen  (which  oxidises).  The  latter  in  excess  is  most  dangerous. 
In  no  case  must  a  hard  or  steel  wire  be  used  for  cleaning  out  the 
blowpipe  nozzle.  A  piece  of  copper  wire  would  suit.  If  the  nozzle 
of  the  blowpipe  is  only  minutely  enlarged,  it  causes  disarrangement, 
and  the  blowpipe  does  not  work  satisfactorily. 

Welding-rods  for  use  on  iron  and  steel  are  composed  of  pure 
iron  in  the  form  of  wire,  in  the  various  sizes  for  the  thickness  of  metal 
welds.  By  using  a  pure  iron  rod,  the  line  of  weld  will  also  be  pure 
(providing  the  welding  has  not  been  oxidised).  All  metallurgists 
are  fighting  against  the  inclusion  of  phosphorus,  sulphur,  and  silicon 
in  the  manufacturing  of  steel  and  iron ;  therefore  operators  must 
also  fight  against  allowing  these  impurities  to  find  their  way  into  a 
weld.  A  good  flux  for  iron  and  steel  is  as  follows : 


Borax  . .          . .  3  parts 

Colophony    .  .          .  .  2     ,, 
Pulverised  glass      . .  3     ,, 
Steel  filings  . .         .  .  2     ,, 
Carbonate  of  potash  1  part 
Hard  soap  powder  . .  1     ,, 


"Melt  in  an  earthenware  vessel. 


IRON  AND  STEEL  119 

One  cannot  be  too  particular  in  preventing  these  impurities  in 
the  welding  line.  None  but  the  purest  rods  must  be  employed. 
They  are  to  be  got  if  the  price  is  paid.  One  must  not  expect  to 
obtain  pure  charcoal  wire  without  paying  for  the  purity.  The  extra 
cost  is  saved  in  many  ways.  The  welding  is  faster,  very  much 
stronger,  and  almost  free  from  oxide.  There  is  no  going  over  the 
weld  twice,  and  no  burning,  as  it  melts  freely.  Finally,  the  weld  is 
neater. 


CHAPTER  XXI 
CAST  IRON 

CAST  iron  is  the  cheapest  and  most  abundant  form  in  which  metal 
is  met  with  in  commerce.  It  is  fusible  at  a  temperature  which  can 
readily  be  attained ;  and,  as  it  receives  remarkably  clean  and  exact 
impressions  of  a  mould,  it  can  be  cheaply  produced,  even  in  very 
intricate  forms.  Its  tensile  strength,  varying  from  an  average  of 
about  7  tons  per  square  inch  in  common  castings  to  upwards  of 
15  tons  with  special  mixtures,  is  ample  for  many  purposes.  Its 
crushing  strength  is  greater  than  any  other  material,  reaching  a 
maximum  of  about  100  tons  per  square  inch.  Being  protected  by  a 
skin,  cast  iron  resists  atmospheric  influences  better  than  wrought 
iron  or  steel,  while,  for  wearing  surfaces  for  machinery,  nothing  is 
superior  to  cast  iron  on  cast  iron  as  sufficient  area  is  provided. 

Castings  are  much  more  easily  and  cheaply  produced  than  forg- 
ings,  so  that  the  latter  are  only  employed  where  special  requirements 
or  strength  and  ductility  render  their  adoption  necessary.  As 
compared  with  steel  castings,  the  advantages  of  cast  iron  for  ordinary 
uses  include  not  only  the  cheapness  of  the  original  material,  but  also 
the  diminished  cost  in  the  preparation  of  the  moulds,  the  smaller 
loss  in  casting,  and  the  saving  of  expense  and  the  time  required  for 
annealing,  which  is  necessary  for  steel,  but  not  for  cast  iron.  Iron 
castings  can,  therefore,  be  prepared  to  meet  a  pressing  emergency, 
while  their  fine  surfaces,  sharp  edges,  and  pleasing  appearance 
recommend  them  for  general  use.  It  must  be  noted  that,  in  the 
welding  of  castings,  one  must  not  go  over  the  weld  twice,  as  it  has 
an  oxidising  effect  on  remelting,  and  the  portion  of  the  silicon  is 
diminished,  while  the  sulphur  is  at  the  same  time  absorbed  from  the 
blowpipe  gases.  The  natural  effect  of  these  changes  is  shown  in 
the  condition  of  the  carbon,  which,  instead  of  being  almost  wholly 
graphitic,  is  all  combined,  thus  producing  a  hard,  white  iron,  deficient 
in  tenacity,  and  brittle.  The  physical  effects  produced  when  cast 
iron  is  remelted  are  thus  merely  indications  of  chemical  changes 
which  have  taken  place  in  the  material,  whilst  the  nature  of  these 
changes  will  vary  with  the  composition  of  the  iron  employed. 

120 


CAST  IRON 


121 


Effect  of  Size  and  Shape. — The  strength  and  solidity  of  a  casting 
are  affected  by  the  bulk  of  metal  employed,  and  by  the  form  of  the 
casting  made.  When  the  metal  cools  in  a  mould,  a  crystalline  is 
developed,  the  crystals  forming  at  right  angles  to  the  cooling  surface. 
If  this  cooling  surface  be  curved,  the  crystals  interlace,  so  as  to  yield 
a  strong  uniform  structure,  while,  on  the  other  hand,  whenever  a 
sharp  change  of  curvature  takes  place,  a  plane  of  weakness  is 
developed. 

Shrinkage  of  Cast  Iron. — Although  cast  iron,  especially  when  very 
grey,  expands  at  the  moment  of  solidification,  the  subsequent  cooling 


FIG.  02. — TRAMWAY  GEAR  CASE,  OUTSIDE  BEARING  BROKEN  OFF,  SUCCESSFULLY 

WELDED. 

from  a  red  heat  to  the  ordinary  temperature  leads  to  a  still  greater 
contraction.  The  shrinkage  of  castings  is,  however,  by  no  means 
a  constant  quality,  but  varies  with  the  proportions  of  the  castings 
and  with  the  character  of  the  metal  used. 

Hardness  of  Iron. — The  hardness  or  softness  of  cast  iron  is,  in 
many  instances,  of  the  greatest  importance,  as  the  metal  has  to  be 
turned,  planed,  filed,  or  otherwise  worked  with  tools.  When  cast 
iron  has  to  be  turned  or  otherwise  worked,  the  hardness  is  of  con- 
siderable importance,  while  in  some  cases  smoothness  of  surface 
and  general  perfection  of  the  casting  are  of  the  utmost  moment. 
Hard  cast  iron  is  brittle,  deficient  alike  in  crushing,  transverse,  and 
tensile  strength,  and  seldom  gives  good  clean  castings. 


Fie.  .ti;>      PRESS  FRAME  BROKEN  ON  <>\r.  SH>K. 
\\  i>  P  vivii  KI>  \\  mi  T\\  o  2  1  \«'ii    I'. 

Holts  failed  ;uid   \veldiiiL1    \\;i      f] 


lira rlv  all 

in  <  hr  eoi 
( 'omhi 

t  hr  nirlal. 

point.    de: 

bility    an, 

and   lrn<l> 

Thr    e\tr 

rlfrrt  s  art 

On  the  amount.  In  \vhitr  east  iron  eon  <  a  in  i  no-  as  i 
Mir  mrtal  is  brittle,  breaks  with  a,  silvrry  white  fr 
rea.dily,  a.nd  parses  t  hroiio-h  a  pasty  staov  in  fusin 

hard,  and  1 

manent . 

inst  nmirn 

varies    fro 

cent.      Tl 

fusibility 

malleabilii 

power  redi 
to  Mir  a 
present . 

(  iraphit  ie  carbon  is  met 
only  in  east  iron,  and  oeea 
sionally  in  stcrl.  It  rrdnees 
Mir  st  rtMi«2;t  li  of  <  hr  mrtal  l>y 
interposition  l>rlA\rrn  Mir 
part  ieh^s,  but  does  not  alTret 
Mir  i;-ra.ins  of  Mu»  irons  t  hrmsrlvrs.  Tlir  ^rnrraJisat  ion  .-ihovr  as  to 
combined  and  frrr  carbon  only  rxprrssrs  part  of  MK»  truth.  \Ylirn 
\vliil.r  r:is(,  irons.  frr(»  from  mjin.irJiiu^st'.  ace  lir:i,ird  for  a  loiiir  prriod. 


ic.    ill.      PKKSS    I''I;\MI:    \\'I:II>I:D     \r    COST 

OF  f.i  7s.  lid.     \VKI.D  ;{  FEET  LONG    \M> 

I     I  NCII   THICK. 

In  use  for  the  ptst   t  \\  o  and  a,  half  years. 


CAST  IRON  123 

at  a  high  temperature,  but  below  fusion,  embedded  in  red  hematite, 
the  characteristic  brill  lencss  is  lost,  and  they  become  more  or  less 
malleable. 

In  connection  with  the  influence  of  cooling,  cast  iron  obeys  the 
law*  which  govern  other  solutions,  for  it  is  well  known  that  slow 
cool  inn  assists  the  production  of  crystals,  and  leads  to  the  production 
of  I -M-ger  size,  while  with  rapid  cooling  both  solvent  and  substance 
dissolved  may  solidify  together.  In  a  similar  manner  slow  cooling 
lends  to  produce  graphitic  carbon,  and  the  slower  the  cooling  the 
larger  1  he  Hakes  of  graphite  which  separate.  Some  kinds  of  white 
iron  may  thus  be  rendered  grey  by  slow  cooling,  while  some  kinds 
of  grey  iron  may  be  made  perfectly  white  by  rapid  cooling  or 
vw  chilling/' 

That  the  carbon  which  exists  in  grey  iron  is  in  the  graphitic  form 
cM.ii  be  proved  by  many  simple  tests.  Thus,  if  finely  divided  white 
iron  be  rubbed  between  the  fingers,  it  is  clean  to  the  touch,  while  grey 
iron  produces  a  smooth  black  coaling  on  the  skin,  exactly  like  that 
due  to  plumbago.  It  has  been  shown  that  nearly  pure  graphite 
ran  be  separated  from  grey  iron. 

All  cast  irons  contain  silicon,  in  quantities  varying  in  ordinary 
cases  from  under  0-f>  to  over  I  per  cent.  A  small  addition  of  silicon 
eliminates  blowholes,  and  produces  sound  castings.  As  soon  as  the 
met  ,i,l  is  sound,  with  the  least  graphite,  the  greatest  crushing  strength 
is  obtained.  This  condition  also  gives  the  maximum  density. 
The  further  addition  of  silicon  leads  to  graphitic  formation, 
diminishes  the  brittleness,  and  gives  the  greatest  transverse  and 
1  ensile  strength.  White  iron  shrinks  during  solidification  more  than 
grey  iron,  while  highly  siliceous  iron  shrinks  still  more  than  white. 
Hence,  on  adding  silicon  to  whit  e  iron,  the  shrinkage  is  diminished ; 
but  an  excess  of  silicon,  on  the  other  hand,  leads  to  increased 
shrinkage.  Shrinkage  appears  closely  to  follow  the  hardness  of  cast- 
iron,  hard  irons  almost  invariably  shrinking  most;  and  as  hardness 
and  shrinkage  depend  upon  the  proportion  of  carbon,  they  may  be 
regulated  by  a,  suitable  addition  of  silicon. 

Cast  iron  is  a,  granular  and  crystalline  compound  of  iron  and 
carbon,  more  or  less  mixed  with  uncombined  carbon  in  the  form 
of  graphite,  but  never  contains  more  than  ~>  per  cent.  It  is  harder 
than  pure  iron,  most  bril  1  le,  and  not  SO  tough.  The  modes  of  com- 
bination  of  the  carbon  with  the  metal,  as  well  as  the  nature  and 
proportion  of  foreign  matters,  such  as  silicon,  aluminium,  sulphur, 
phosphorus,  and  manganese,  determine  the  infinitely  varying  quali- 
ties according  <<>  the  colour,  degree  of  fusibility,  hardness,  tenacity, 


124  MODERN  METHODS  OF  WELDING 

and  so  on.  All  cast  irons  are  not  available  for  foundry  purposes. 
In  grey  cast  iron  the  carbon  is  mechanically  interspersed  in  small 
black  specks  among  the  lighter  particles  of  metals,  the  fracture  being 
a  dark  grey  colour,  and  being  of  granular  or  scaly  crystalline  char- 
acter. Grey  iron  is  much  softer  and  tougher  than  white  iron,  and 
may  be  filed  and  turned. 

In  white  cast  iron  the  greater  part  of  the  carbon  is  present  in 
the  form  of  a  chemical  combination — carbide  of  iron — and  white 
iron  is  very  brittle,  and  can  neither  be  turned  in  a  lathe  nor  filed. 
Grey  cast  iron  requires  a  higher  degree  of  heat  before  it  commences 
to  fuse,  but  becomes  very  liquid  at  a  sufficiently  high  temperature. 
It  is  important  to  remember  this  point  when  castings  are  being 
welded,  especially  when  inclined  from  the  horizontal,  as  the  metal 
would  run  away  from  the  weld.  White  cast  iron  is  not  so  easy  to 
weld.  It  does  not  flow  well,  is  rather  pasty  in  consistence,  and  scintil- 
lates as  it  flows  in  the  molten  state.  White  cast  iron  is  silvery- 
white,  either  granular  or  crystalline,  difficult  to  melt,  brittle,  and 
excessively  hard.  It  is  a  homogeneous  chemical  compound  of  iron 
with  from  2  to  4  per  cent,  of  carbon.  Granular  cast  iron  can  be  con- 
verted into  grey  cast  iron  by  fusion  and  slow  cooling,  whilst  grey 
cast  iron  can  be  converted  into  granular  white  cast  iron  by  fusion 
and  sudden  cooling.  Crystalline  white  iron  is  harder  and  more 
brittle  than  granular,  and  is  not  capable  of  being  converted  into 
grey  cast  iron.  Grey  cast  iron  contains  about  1  per  cent.,  or  less, 
of  carbon  in  chemical  combination  with  the  iron,  and  from  1  to  4 
per  cent,  of  carbon  in  the  state  of  graphite  in  mechanical  mixture.^ 
The  larger  the  proportion  of  graphite  the  weaker  and  more  pliable  * 
is  the  iron. 

The  following  remarks  upon  some  points  already  described  may 
aid  in  roughly  estimating  the  quality  of  cast  iron. 

When  the  colour  is  uniform  dark  grey,  the  iron  is  tough,  providing 
there  is  also  high  metallic  lustre.  If  there  be  no  metallic  lustre  the 
iron  will  be  easily  crumbled.  The  weakest  sort  of  cast  iron  is  where 
the  fracture  is  of  dark  colour,  mottled,  and  without  lustre.  The 
iron  may  be  accounted  hard,  tenacious,  and  stiff  when  the  colour 
of  the  fracture  is  lightest  grey,  with  a  high  metallic  lustre.  When 
the  colour  is  light  grey,  without  metallic  lustre,  the  iron  is  hard  and 
brittle.  When  the  colour  is  dull  white,  the  iron  is  still  more  hard 
and  brittle  than  in  the  last  case.  When  the  fracture  is  greyish- 
white,  interspersed  with  small  radiating  crystals,  the  iron  is  of  the 
extreme  degree  of  hardness  and  brittleness. 

When  cast  iron  is  dissolved  in  muriate  of  lime  or  muriate  of  mag- 


CAST  IRON  125 

Inesia,  the  specific  gravity  is  reduced  to  2-155.  Most  of  the  iron  is 
[removed,  and  the  remainder  consists  of  graphite  with  the  impurities 
[of  cast  iron.  The  soft  grey  iron  yields  to  the  file  after  the  outer 
I  crust  has  been  removed.  The  quality  of  the  iron  in  a  melted  state 
is  really  judged  by  the  practised  eye  from  the  nature  of  the  agitated 
aspect  of  its  surface.  The  mass  of  fluid  seems  to  undergo  a  circula- 
tion within  itself,  having  the  appearance  of  ever-varying  network. 

When  this  network  is  minutely  subdivided,  it  indicates  soft  iron. 
If,  on  the  other  hand,  crystals  be  thrown  up  in  convolutions,  the 
quality  of  the  metal  must  be  hard. 

One  of  the  most  important  points  in  the  welding  of  cast  iron 
is  not  to  go  over  the  weld  twice,  as  each  time  any  part  is  melted 
more  than  once,  the  graphite  burns  out  and  leaves  white  iron,  which 
is  hard  and  brittle.  One  must  remember  that  every  additional 
melting  of  cast  iron  injures,  or  is  likely  to  injure,  its  quality  as  a 
structural  material  by  the  addition  of  foreign  substances.  These 
reduce  the  value  of  the  coefficient  of  resistance  at  rupture  and  may, 
or  may  not,  reduce  that  of  ultimate  extension.  That  is,  the  metal 
by  remelting  becomes  weaker,  and  may  become  more  brittle. 

The  numerous  failures  which  puzzle  operators  in  the  welding  of 
cast-iron  articles  are  often  due  to  lack  of  knowledge.  They  have 
not  made  themselves  acquainted  with  the  metal  they  are  welding. 
It  is  a  sine  qua  non  that,  if  they  are  to  become  proficient  operators, 
they  must  have  the  necessary  metallurgical  knowledge,  so  as  to 
know  exactly  what  are  the  constituents  of  the  metal  being  welded. 
The  state  of  the  carbon  in  the  metals  depends  on  whether  welds  are 
of  grey  iron.  It  is  necessary  for  every  welder  to  study  thoroughly 
the  causes  that  facilitate  or  prevent  the  precipitation  of  the  carbon 
in  the  form  of  graphite.  The  rapid  cooling  of  the  molten  metal  in 
fusion  will  bring  about  the  combination  of  the  carbon  and  the  iron. 
This  forms  white  iron,  which  is  hard  and  brittle,  and  cannot  be 
machined  or  filed. 

Welding  of  cast  iron  is  a  simple  process,  and  with  an  experienced 
man,  who  has  knowledge—metallurgical  and  chemical— of  the 
article  he  has  to  weld,  failure  is  impossible.  The  repair  on  the  line 
of  welding  is  generally  of  a  superior  quality  to  the  rest  of  the  casting, 
owing  to  the  metal  added  being  purer  and  the  weld  well  carried 
out  and  free  from  blowholes.  Cast  iron  consists  of  metallic  iron, 
together  with  at  least  1-5  per  cent,  of  carbon.  It  also  contains 
sulphur,  silicon,  phosphorus,  manganese,  and  other  elements  in 
greater  or  less  proportion;  but  these,  as  indicated  above,  may  be 
regarded  as  impurities.  The  proportion  of  elements  other  than 


126  MODERN  METHODS  OF  WELDING 

iron  is  usually  about  7  per  cent,  of  the  total  weight.     Cast  iron  is 
fusible  at  a  temperature  of  about  1,200°  C.     When  cold  it  is  hard 
and  brittle.     It  is  not  malleable  or  ductile,  nor  can  it  be  hardened 
or  tempered  like  ordinary  carbon  steel.     Cast  iron,  when  fused,  con- 
sists of  saturated,  or  nearly  saturated,  solution  of  carbon  in  iron. 
The  amount  of  carbon  which  molten  iron  can  thus  dissolve  is  about 
3J  per  cent,  of  its  own  weight,  though  the  solubility  is  largely  in- 
fluenced by  the  presence  of  other  elements.     As  long  as  iron  con- 
taining some  3  per  cent,  of  carbon  remains  in  the  fused  condition,  the 
composition  is  uniform  throughout,  and  the  carbon  has  no  tendency 
to  separate  from  the  metal  except  with  very  grey  iron.     In  this  case 
a  layer  of  graphite  may  be  formed.     But  when  molten  cast  iron  is 
cooled  to  a  temperature  at  which  it  begins  to  solidify,  it  may  either 
retain  the  carbon  and  solidify  in  a  relatively  homogeneous  form, 
called  white  iron,  or  may,  in  solidifying,  precipitate  the  greater  part 
of  the  carbon  in  the  form  of  small  scales  of  graphite  which,  being 
entangled  by,  and  uniformly  distributed  through,  the  iron,  imparts 
to  it  a  somewhat  spongy  nature,  and  produces  the  dark  colour  and 
soft  character  met  with  in  grey  iron.     The  condition  which  the 
carbon  assumes  on  the  solidification  of  the  mass  is  dependent  partly 
on  the  rate  of  cooling,  and  still  more  on  the  nature  and  quantity  of 
the  associated  elements. 

In  the  early  stages  of  the  oxy-acetylene  process  it  was  generally 
considered  that  cast  iron  and  cast  steel  could  not  be  welded  by  this 
process.  The  author,  over  fifteen  years  ago,  welded  castings  by  this 
process  nearly  daily,  and  executed  some  very  important  castings 
with  success.  At  this  period  he  found  out  how  valuable  and  neces- 
sary was  the  preheating  furnace  for  counteracting  the  phenomenon 
of  expansion  and  contraction.  Since  then  it  has  been  recognised 
that  the  only  way  of  getting  satisfactory  castings  welded  is  by  the 
use  of  a  heating  furnace,  both  for  preheating  before  welding  and 
for  annealing  after  welding,  allowing  the  casting  to  cool  very  slowly. 
Failure  is  almost  impossible  if  this  is  carried  out,  provided  the  weld 
has  been  properly  executed. 

Of  late  years  operators  and  employers  have  been  getting  more 
enlightened  on  welding  processes,  and  most  are  now  providing  these 
necessary  appliances.  Also  all  operators  are  now  taking  technical 
courses  at  the  various  schools.  Cast  iron,  in  the  author's  opinion, 
is  the  easiest  of  all  metals  to  weld.  With  a  little  practice,  combined 
with  technical  knowledge,  operators  are  soon  able  to  do  intricate 
jobs;  and  the  welded  part,  if  done  well,  is  generally  better  than  the 
other  parts  of  the  casting,  because  the  material  added  by  the  weld- 


CAST  IRON  127 

ing-rod  is  purer  in  its  mixture,  and  should  thus  be  better  metal. 
Cast  iron  cannot  be  forged,  but  articles  are  cast.  They  are  not  malle- 
able or  ductile.  The  majority  of  castings  in  iron  should  be  capable 
of  being  worked — that  is,  they  must  be  soft  metal  when  finished 
and  able  to  be  filed  or  machined.  The  metal  of  grey  castings  is 
usually  grey  iron.  The  description  at  the  beginning  of  this  article 
should  be  studied  thoroughly.  One  must  remember  that  the  rapid 
cooling  of  the  metal  in  fusion  brings  about  the  combination  of  the 
carbon  and  the  iron,  which  means  the  formation  of  white  iron. 
Slow  cooling  and  reheating  bring  about  precipitation  of  the  carbon 
and  grey  iron. 

The  melting-point  of  cast  iron  is  1,200°  C.,  but  its  oxide  melts 
at  1,350°  C.  This  is  an  important  point,  and  in  melting,  the  oxide 
usually  flows  on  the  top  of  the  weld,  where  it  can  be  removed  either 
by  a  flux  or  (if  the  welder  be  experienced)  by  the  welding-rod, 
scraping  it  over  the  surface  horizontally.  If  the  flame  is  held  too 
long  on  the  casting  after  the  metal  is  molten,  the  metal  burns  and 
oxidises,  the  silicon  is  volatilised,  the  carbon  decarbonised,  and  the 
weld  will  be  hard  and  cannot  be  machined  or  filed.  When  cast- 
iron  articles  are  welded  the  welding  flame  causes,  to  a  certain  extent, 
a  volatilisation  of  the  silicon,  which  is  contained  in  the  metal  in 
proportion  from  0-5  to  4  per  cent.,  generally  about  2  per  cent. 
If  this  is  burnt  out,  it  is  necessary  to  replace  the  loss,  which  is  done 
by  the  welding-rod,  which  should  contain  5  per  cent,  of  silicon. 
Therefore,  as  welding  takes  place,  the  rod  with  the  increased  per- 
centage of  silicon  gives  back  to  the  casting  the  percentage  that  has 
been  volatilised  out.  This  material  usually  leaves  the  welded  lin- 
soft,  so  that  it  may  be  machined  or  filed. 

Of  the  difficulties  experienced,  the  first  is  the  expansion  and  con- 
traction. Owing  to  the  metal  being  non-ductile,  and  devoid  of  those 
elements  for  elongation  and  elasticity,  castings  are  difficult  to  handle. 
The  only  remedy  is  preheating  in  a  furnace,  and  annealing  after 

welding. 

The  second  difficulty  is  to  prevent  the  line  of  welding  becornu 
hard.     To  stop  this  the  weld  must  be  made  at  the  first  trial,  and 
must  not  be  gone  over  a  second  time.     The  welding  must  also  I 
sharp,  as,  if  the  blowpipe  is  kept  on  too  long,  it  is  burnt  an 

weld  hard. 

Thirdly  the  temperature  of  the  casting  must  be  brought  up  ; 
the  furnace  to  between  850°  and  900°  C.  before  any  welding  takes 
place      If   it  is  lifted  from  the  furnace  to  the  welding  table, 
must  be  done  quickly,  and  quickly  welded,  and  returned  to  the 


128  MODERN  METHODS  OF  WELDING 

annealing  furnace  before  the  heat  of  the  casting  gets  below  the 
850°  C.  Below  this  temperature  the  forces  of  expansion  and 
contraction  begin  to  come  into  action,  and  internal  strains  will 
at  once  be  set  up,  which  may,  in  a  few  minutes,  if  the  tempera- 
ture is  much  below  850°  C.,  crack  or  fracture  in  the  casting;  it  is 
not  necessary  in  the  weld.  In  some  cases,  the  internal  strains  remain 
in  the  castings  without  fracture,  until  the  casting  becomes  quite 
cold,  when  the  fracture  from  the  release  of  the  internal  strains  occurs. 

After  welding,  and  putting  the  casting  into  the  furnace,  it  must 
at  once  be  seen  to  that  the  temperature  of  the  furnace  is  raised  (if  it 
is  not  already  raised  as  it  should  be)  to  950°  C.  This  is  so  that  the 
casting  after  welding  can  be  raised  to  this  heat  quickly,  to  bring 
the  parts  of  it  up  to  one  heat,  since  the  part  that  had  been  welded 
was  very  much  hotter  than  the  part  not  welded.  Thus  one  can  stop 
uneven  contraction  when  the  casting  is  being  cooled  off.  After 
the  heat  has  been  raised  to  950°  C.,  which  would  not  be  long  if  the 
furnace  is  working  as  it  ought  to,  the  furnace  must  be  cooled  right 
down  to  cold  before  removing  the  casting. 

Some  illustrations  of  preheating  and  annealing  are  given  in 
previous  chapters  relating  to  expansion  and  contraction.  They 
should  be  carefully  studied. 

Fourthly  come  the  difficulties  of  lack  of  penetration,  bad  joining, 
sinking  of  the  surfaces,  blowholes,  and  interposition  of  oxide. 
Lack  of  penetration  is  a  frequent  occurrence.  There  is,  however, 
no  justification  for  it,  if  operators  will  only  go  to  the  bottom  of  the 
weld  in  all  cases.  The  blowpipe  must  be  kept  on  the  particular 
welding  line,  until  such  time  as  the  bottom  is  melted.  When  the 
bottom  is  found  at  the  starting-point,  there  should  be  no  mistake 
about  the  line  being  continued  from  the  bottom  of  the  weld. 

Interposition  of  oxide  is  a  common  occurrence,  but  it  is  one  which 
can  easily  be  avoided.  It  occurs  through  using  an  excess  of  oxygen, 
making  the  molten  metal  oxidised  too  liquid  and  too  hot,  and 
through  being  too  long  on  welding  and  going  over  it  more  than  once. 
The  oxide  forming  through  these  errors  is  imprisoned  in  the  metal. 
Therefore,  it  is  not  homogeneous,  and  the  weld  is  defective.  This 
will  not  come  about  if  the  operator  will  first  of  all  bevel  the  joint 
where  it  has  to  be  welded.  When  it  is  ready  and  heated,  welding 
must  take  place  at  once  by  commencing  on  the  bottom  of  the  bevel. 
As  soon  as  this  is  melted,  add  the  welding-rod,  previously  heated, 
in  the  bevel,  move  the  blowpipe  forward  with  an  elliptical  sweep, 
keeping  it  close  in  the  line  of  metal.  Do  not  let  the  white  tip  touch 
the  metal,  but  keep  it  about  ^  inch  from  it,  and  go  steadily  and 


CAST  IRON 


129 


slowly  forward,  filling  up  the  bevel  uniformly  with  the  feeding- 
rod  until  the  end  of  the  weld  is  reached.  There  must  be  no  stoppage 
whatever,  while  welding  the  line  prepared.  If  you  stop  your 
weld  will  be  hard  and  cannot  be  filed  or  machined.  If  it  is  done 
quickly,  and  filled  in  as  the  welding  proceeds,  with  no  stoppage, 
the  weld  will  be  a  success,  neat,  strong,  and  easy  to  work. 

If  the  article  to  be  welded  is  a  complete  casting  with  a  break, 
then  it  would  be  necessary  to  bevel  the  fracture  on  both  sides  before 
welding:  such  a  case  is  a  motor  cylinder  broken  on  the  flanges. 
The  one  illustration  below  would  require  bevelling;  and  take  care 
that  the  weld  is  thoroughly  penetrated. 

Welding-rods  used  for  cast  iron  should  be  made  more  or  less 
from  good  tough  metal, 
with  a  fine  granular 
,  structure,  and  free  from 
impurities,  especially 
manganese.  They 
should  be  incorporated 
with  silicon,  in  two 
grades,  one  to  have  2-9 
per  cent,  and  the  other 
to  have  4-1  per  cent, 
of  silicon.  The  object 
of  this  grading  is  very 
important,  as  the  one 
has  a  large  granular 
structure,  and  the  other 

has  a  fine  granular  structure.  The  latter  would  be  used  on  heavy 
machinery  work,  and  the  former  on  smaller  castings,  such  as  motor- 
car cylinders,  which  are  cast  from  fine  granular  material. 

All  founders  grade  their  metal  in  this  manner.  They  do  not 
use  the  same  for  both  light  and  heavy  castings.  Therefore  it 
is  imperative  that  the  welding-rods  should  be  made  in  accordance 
with  the  general  specifications  of  the  general  castings;  and  they 
should  be  very  smooth  and  regular  in  thickness,  which  should  be 
from  ^  inch  diameter  rising  by  TV  inch  diameter  to  -J-  inch  diameter. 

They  should  be  20  inches  long,  and  should  be  all  sand-blasted, 
after  they  are  cast.  This  is  an  important  point.  Otherwise  the  rods 
will  be  all  rough  and  covered  with  sand,  which  is  very  detrimental 
to  the  weld.  No  welding-rods  must  be  used  which  have  not  had 
the  moulding  sand  removed;  nor  must  welding-rods  be  used  that 
have  been  cast  in  solid  moulds,  as  they  would  be  chilled  and  hard. 


FIG.  65. — TWO-CYLINDER  MOTOR  ENGINE  BROKEN. 


130 


MODERN  METHODS  OF  WELDING 


It  is  not  agreed  in  the  welding  trade  that  fluxes  are  necessary 
for  the  oxy-acetylene  welding  of  cast  iron.  The  author  does  not 
advise  the  use  of  any  flux  whatever,  in  general.  But  there  are  a  few 
cases  in  which  a  flux  is  of  great  assistance — e.g.,  where  castings  are 
old,  or  are  full  of  sand  and  slag.  This  will  only  occur  where  cheap 
castings  are  made.  The  method  of  using  the  flux  is  to  dip  the 
end  of  the  rod  into  flux,  which  should  be  near  to  hand  and  to  the  rod 
being  heated.  The  flux  must  not  be  thrown  into  the  molten  weld, 
as  too  much  would  make  the  weld  hard,  so  that  it  could  not  be 
worked. 

The  illustration  (Fig.  67)  shows  a  good  test  of  cast-iron  welding 
— a  water  pump  accidentally  broken  while  being  worked  in  the 

shop.      It   was   welded    in    thirty-six 
minutes. 

The  method  of  execution  was  as 
follows:  The  casting  was  first  bevelled 
with  a  diamond-point  chisel,  the  metal 
being  TSF  inch  thick.  The  gas  furnace 
had  already  been  lit.  The  casting  was 
placed  on  a  sliding  grid,  which  fitted  on 
the  sides  of  the  furnace.  This  sliding 
grid,  with  casting  placed  and  fixed  in 
position,  was  lifted  by  a  small  swinging 
hand-crane,  hoisted  by  a  rope,  and 
swung  round  to  the  furnace,  when  the 
grid  was  pushed  into  the  furnace.  The 
casting  was  covered  with  an  asbestos 
"shawl,"  and  the  door  closed.  The  tem- 
perature was  then  at  550°  C.  Another 

burner  was  lit,  and  the  temperature  rose  to  950°  C.  in  thirty-five 
minutes  Half  the  burners  were  put  out,  and  the  sliding  grid,  with  the 
casting  still  fixed,  was  lifted  by  the  crane  and  placed  on  the  welding 
table.  The  blowpipe,  already  in  position,  was  lit,  and  the  welding 
started,  and  was  continued  without  interruption  or  without  going 
over  any  part  of  the  weld  twice.  The  grid  was  then  attached  to  the 
crane,  which  swung  the  casting  back  to  the  furnace.  The  door  was 
closed  and  the  two  burners  lit  till  the  temperature  (then  800°  C.)  was 
raised  to  950°  C.  (this  occupied  only  thirty-six  minutes  from  the 
time  the  furnace  door  opened  to  take  it  out  till  the  door  closed  for 
annealing).  Then  the  burners  were  turned  right  out,  and  the  cast- 
ing was  allowed  to  cool  slowly  overnight.  The  result  was  a  first- 
class  job,  strong,  well-annealed,  and  with  no  distortion. 


FIG.  66. — Two  CYLINDEBS 
WELDED  COMPLETE. 


CAST  IRON  13) 

The  field  for  welding  such  castings  is  enormous.  The  demand 
is  greater  than  the  supply.  There  are  few  operators  able  to  do  al! 
jobs  as  they  come  along.  If  they  had  scientific  and  technical  train- 
ing, which  should  be  followed  up  with  practical  work,  they  would 
become  proficient,  and  would  be  able  to  do  any  class  of  work  The 
possibilities  of  welding  broken  castings  are  great,  and  almost  any 
repair  can  be  done.  A  few  articles  here  are  shown  which  can  be  and 
have  been  welded  by  this  process.  Good  jobs  can  always  be  done  if 


FIG.  67. — BROKEN  TWO-CYLINDER  WATER  PUMP. 

operators  carry  out  carefully  the  instructions  given.  I  may  repeat 
that  in  all  cast-iron  weldings,  if  success  is  to  be  attained,  the  article 
must  first  be  prepared,  must  be  preheated  (free  from  air)  to  a  tempera- 
ture of  950°  C.,  welded  with  the  purest  welding-rod,  returned  to  the 
annealing  furnace  when  the  casting  gets  down  to  850°  C.,  whether 
the  casting  is  finished  or  not,  and,  if  it  is  necessary  to  weld  further, 
must  be  brought  up  again  to  a  temperature  of  950°  C.  It  can  be 
taken  out  for  welding,  and  afterwards  returned  to  the  furnace  and 
allowed  to  cool  slowly,  free  from  air. 


CHAPTER  XXII 
DISSOLVED  ACETYLENE 

DISSOLVED  acetylene,  sometimes  called  high-pressure  acetylene, 
is  being  greatly  used,  owing  to  its  convenience,  the  purity  of  its 
acetylene,  the  equal  pressure  and  proper  mixture  of  the  two  gases. 
the  regularity  of  flame,  the  absence  of  oxidising  or  carbonising,  the 
well-maintained  sharp  cone  at  the  tip,  and  the  continuous  welding 
till  the  cylinder  is  empty. 

Dissolved  acetylene  is  acetylene  in  its  purest  form,  compressed 
after  purification  into  cylinders  containing  an  absorbent  material. 
The  gas  is  first  generated  in  an  ordinary  carbide-to-water  type  in 
which  the  carbide  falls  in  large  volumes  of  water  in  order  to  prevent 
overheating  of  the  gas  and  to  maintain  within  the  generator  a  tem- 
perature considerably  below  that  at  which  local  polymerisation  of 
the  gas  can  occur.  Otherwise  the  heat  of  dissociation,  which  repre- 
sents 1-65  per  cent,  of  the  total  heating  value  of  the  gas,  and  is 
responsible  for  the  phenomenal  heating  value  of  the  acetylene  flame, 
is  liberated  either  wholly  or  in  part  during  generation,  and  is  there- 
fore not  available  in  the  flame ;  in  that  case  further  local  polymerisa- 
tion takes  place,  and  the  tarry  residues  mix  with  the  water  and  the 
gas  and  make  the  latter  impure.  The  acetylene,  after  generation, 
must  be  treated  by  numerous  processes  in  order  to  extract  the  impuri- 
ties. These  impurities  are  in  three  forms — gaseous,  liquid,  and  solid. 
There  is  no  single  process  capable  of  dealing  effectively  with  the 
three.  The  gases  must  be  treated  with  at  least  six  processes  of 
purification,  two  of  which  must  be  mechanical,  four  chemical. 
All  chemicals  must  be  incapable  of  producing  overheating  of  the 
acetylene  undergoing  purification.  Special  precautions  must,  at 
all  times,  be  maintained  to  preclude  the  possible  admixture  of  air 
with  the  acetylene.  All  purifiers  and  the  acetylene,  after  purifica- 
tion, should  be  tested  twice  daily  in  order  to  secure  complete 
purification. 

The  acetylene  is  then  compressed  into  cylinders  already  prepared 
with  solvent  material.  The  compressors  used  for  this  purpose  are 
multiple  stage  compressors,  with  intermediate  cooling  between 

132 


DISSOLVED  ACETYLENE  133 

each  stage  The  cylinders  of  the  compressors  must  be  wmter- 
jacketed,  and  the  degree  of  compression  in  each  stage  must  not  bo 
capable  of  raising  the  temperature  in  excess  of  100°  C— that  is 
one-sixth  of  the  critical  temperature.  The  gas,  after  compression' 
and  prior  to  entering  the  cylinders,  must  undergo  mechanical  separa- 
tion for  the  extraction  of  final  traces  of  moisture. 

Cylinders  in  which  dissolved  acetylene  is  stored  are  made  from 
the  finest  quality  steel,  and  is  cold-drawn  to  the  shape  of  the  cylinder 
from  a  flat  piece  of  steel,  whilst  the  bottom  and  walls  are  folded  over 
one  another  and  pressed  together  under  a  pressure  of  several  tons 
per  square  inch.  Only  the  finest  and  most 
ductile  quality  of  steel  would  permit  of 
cold-drawing  for  44  inches  in  length.  The 
cylinder  walls,  only  -^  inch  thick,  although 
only  intended  for  use  under  a  pressure  of 
about  200  pounds  per  square  inch,  are  made 
to  stand  a  pressure  of  1,000  pounds  per 
square  inch.  As  is  well  known,  acetylene 
gases  can  only  be  stored  under  pressure 
with  safety  when  dissolved  in  a  solvent 
such  as  acetone,  which  must  be  absorbed 
by  a  porous  material  adapted  to  fill  the 
space  in  the  containing  vessel. 

Government  regulations  require  that 
the  porosity  of  the  absorbent  material  in 
the  container  shall  not  exceed  80  per  cent., 
and  shall  be  homogeneous  through  the 
material  without  any  free  gas  space.  In 
the  past  it  has  been  customary  to  employ, 
as  the  absorbent  body  granulated,  solid 
material  such  as  charcoal,  or  an  animal 
filament,  such  as  silk,  but  these  substances 
are  subject  to  certain  disadvantages.  Granulated  charcoal  and  ot  her 
solid  materials  tend  to  disintegrate  into  dust  by  attrition  of  the  par- 
ticles, if  the  container  is  subjected  to  repeated  vibration  or  bumping. 
This  disintegration  creates  free  gas  space  and  also  dust  particles,  which 
are  liable  to  blow  forward  with  the  gas  and  block  the  container  valve 
or  the  nozzle  of  the  blowpipe  employed  when  the  dissolved  acetylene 
is  used  for  welding.  Silk,  owing  to  its  fibrous  nature,  does  not  dis- 
integrate, but,  on  the  other  hand,  it  is  not  sufficiently  resilient  to 
obviate  packing,  and  saturated  with  the  liquid  solvent  and  subjected 
to  repeated  vibration  and  bumping.  The  consequence  is  that  free 


FIG.  68. — PERFECT  NEUTRAL 
FLAME. 

When  blowpipe  is  working 
properly,  the  length  of  the 
small  white  cone  isas  shown . 
In  the  patent  "  D.A."  blow- 
pipe, the  numbers  on  the  t  ip 
correspond  to  the  consump- 
tion of  acetylene  in  lit  i 
hour. 


134  MODERN  METHODS  OF  WELDING 

gas  space  may  be  created  after  the  container  has  once  been  packed 
to  the  prescribed  porosity  and  put  in  use. 

There  has  since  been  patented  an  improved  method  of  storing 
compressed  acetylene  gas.  This  patent  was  taken  out  by  Thomas 
Gaskel  Allen,  of  London,  July  27,  1916.  The  object  of  the  invention 
is  to  provide  a  new  type  of  filling  material,  superior  to  that  used  in 
the  past.  According  to  the  material  employed,  it  is  sometimes 
known  as  "  kapok  "  (Javanese  fibre),  or  Indian  kapok.  One  form 
suitable  for  the  purpose  of  this  invention  is  the  Eriodendron 
anfractuosum,  but  the  invention  covers  any  suitable  variety  of 
kapok.  Using  this  material,  a  much  smaller  weight  than  previously 
is  necessary  to  obtain  a  porosity  of  805  in  the  container. 

Further,  kapok  has  a  tendency  to  swell  when  it  absorbs  the  liquid 
solvent,  thus  precluding  altogether  the  possibility  of  free  gas  space 
forming  within  the  container  after  it  has  been  once  packed  to  the 
required  porosity.  On  examination  with  the  microscope,  the  central 
tube,  filled  with  air,  gives  to  fibres  or  kapok  its  very  valuable  light- 
ness. The  fibres  are  absolutely  impermeable  by  water,  owing  to 
the  presence  of  wax  with  which  the  filaments  are  coated.  They  will 
support  from  thirty  to  thirty-five  times  their  own  weight  in  water. 
Ordinary  cork  will  only  float  five  times  its  weight.  This  special  fibre, 
when  used  as  a  filling  material,  cannot  disintegrate  into  dust,  no 
free  gas  space  can  be  created  by  constant  vibration,  and  no  dust  can 
pass  through  the  blowpipe. 

Dissolved,  acetylene  compressed  in  cylinders  provides  a  definite 
volume  of  acetylene  of  the  highest  purity,  at  a  constant  pressure, 
controlled  by  a  regulator  fixed  on  the  oxygen  cylinder  valve.  This, 
together  with  the  oxygen  in  equal  volumes  and  at  equal  pressures, 
gives  a  wide  range  for  welding.  The  clear  flame  obtained  is  shown 
in  Fig.  68. 

The  cone  should  not  be  allowed  to  touch  the  metal,  but  should  be 
held  so  that  the  required  heat  is  obtained  without  burning  the  work. 
When  stopping  the  blowpipe,  always  turn  off  the  oxygen  first. 
This  system  has  many  advantages  over  the  low-pressure  process. 
The  gas  is  always  ready  for  use  without  waste  of  time  in  preparation, 
and  when  shut  off  it  can  be  stored  indefinitely  without  loss.  It  is 
handled  with  the  greatest  ease,  and  can  be  used  in  any  position. 
The  apparatus  is  cheap ;  >the  handling  of  carbide  and  water  and  the 
necessity  of  removal  of  residue  are  eliminated.  There  is  no  danger 
to  the  operator,  and  no  bad  smell,  owing  to  the  purity  of  the  gas. 


CHAPTER  XXIII 
CUTTING  IRON  AND  STEEL 

THE  use  of  oxygen  for  cutting  iron  and  steel  is  being  developed 
enormously;  and  is  being  adopted  everywhere.  The  method  con- 
sists essentially  in  an  ordinary  blowpipe,  with  an  additional  passage 
through  which  an  independent  and  separately  controlled  stream  of 
oxygen  is  supplied  at  the  discretion  of  the  operator.  This  separate., 
supply  of  oxygen  may  be  discharged  through  the  centre  of  the  blow- 
pipe, in  which  case  the  mixed  gases  employed  for  heating  are  con- 
ducted through  an  annulus  surrounding  it;  or  the  supply  may  be 
brought  in  a  passage  immediately  behind  the  heating  flame. 

The  simple  expedient  of  maintaining  an  independent  heatin-j 
jet  in  operation,  whilst  the  cutter  is  travelling,  renders  the  cutting 
operation  continuous.  It  furnishes  the  quantity  of  additional  heat 
necessary  to  render  the  oxide  fluid,  so  that  it  can  be  blown  away 
through  the  cut  by  the  separate  jet  of  oxygen.  The  cutting  opera- 
tion can  be  mastered  by  any  intelligent  workman  in  a  few  hours. 
The  edge  or  surface  of  the  plate  at  the  point  to  be  cut  is  heated  by  t  ho 
mixed  jet  of  oxygen  and  acetylene.  When  this  spot  has  been  brought 
to  a  state  lower  than  the  melting-point,  a  fine  jet  of  oxygen  is  dis- 
charged upon  it.  This  immediately  produces  combustion  of  the 
metal,  with  the  resulting  formation  of  the  oxide.  The  jet  of  ox 
is  made  sufficiently  strong  to  blow  away  this  oxide  in  front  of  it, 
with  the  result  that  a  clean,  narrow  cut  is  effected  through  the  metal 
at  a  speed  of  travel  which  is  comparable  with  hot  sawing.  The 
metal  on  each  side  of  the  cut  is  neither  melted  nor  injured  in  any 
way,  as  the  action  proceeds  too  rapidly  for  the  heat  to  spread. 
In  fact,  the  edges  present  the  sharp  and  purely  metallic  surface  of  a 
saw  cut. 

The  cutting  may  be  made  to  follow  any  desired  linos,  executing 
circles,  curves,  or  profiles  as  desired,  for  which  purposes  guides  and 
other  mechanical  contrivances  are  supplied.  Special  appliann 
supplied  for  ensuring  a  steady  movement  of  the  cutting  nozzle, 
a  matter  of  considerable  importance  where  neat  and  accurate  \\ork 
is  desired.  *he  process  may  be  employed  for  cutting  sections  of  any 

135 


HBTHO 

knees  up  to  1  1  »  uttir.. 

:  ing  point  of  the  metal  should  never  Iv  reached.     Tho  > 

loymont  of  oxygon  for  this  purpose,  therefore.  doj>ends  on  the 

ting-point  of  oxide  being  lo\\er  than  that  of  tho  im •: 

Hie  out  tors  are  made  in  several  varieties      Tho  Brit  is} 

ipany  are   makers   of    tho  one   illustrated   Inflow,    \\hioh 

.1  M;   it  is  a  reliable  artiele  ami  is  largely  DC 
[\ubher  tubing  must   be  fixed  at   O  aiul   //  n 
s   for   heating  are  separately    adjust etl    by   valves    /»'  and    //. 
^  n  re  discharged  thnmgh  the  [massages  7' 

o   resrulatins:   the   supply   of  oxygon   for  outt  parately 

mlKxl  by  moans  of  the  thumb  sere\\  Q  or  the  thumb  K\ 
The  st^rate  jot  of  oxygon  for  outti 
passage  T       .1    is  an   adjustable  sliding  siuide.   \vhioh   eai 


Fu;    ^      H.\\i»-l'i  TTIN  ITE. 

eheil  to  the  eutter  head  at  H.  in  order  to  maintain  a  uniform 

wee  between  the  eutter  and  the  work.     There  are  : 

for  eutting  up  to  (>  inches  thick,  and  a  - 

ohes.     Tho  table  on  p    1:>~  lie  ap]>n>xir 

L^US  thieknesses.  the  consumption  of  oxygon,  and  linen 

hour.  ete. 

Phis  is  a  very  useful  table.     Ojvrators  can  oomj^re  results  from 

r  own  out  ting  by  it. 

»ince  the  [H^ruxi  in  whioh  was  introduced  the  develop- 

t  has  been  rapid.     Here,  again,  the  war  has  brought  this  unique 

ess  into  vast  uses,  whioh  would  have  taken  ten  years  of  i: 

;  to  attain. 

?he  real  theory  o:  cutting  of  iron  and  steel  wa- 

>le  process,  and  was  known  for  years  before  it  became  a  t 

rial  proposition.     It  was  found  in  the  chemical  lab 

thin  strip  of  iron  or  steel  is  plunged  into  a  jar  of  o> 


IKON  AND  STI<;KL  , 

e  ir gnitea  to  incandescence  « 

rigW  away.    This,  then,  U  the  equivalenf  to  cut< steel  1 

II      .'IS    WC  sllil.ll    SCC  ilS    WC  (JO  along. 


Thick 
oj  Plate. 

Cutting 

/, 

Oxygen 

/'/, 

"./'  (  '•"/'./<  a 

per  linn, 

Feet  of 
M.hd  (',,1, 

'/>!>'  llnlir 

Comumplit 

of  (}.r//(/i  / 

per  Foot  < 

1  in  i 

Inches. 



\ 

24 

4H 

65 

0-75 

28 

60 

60 

82 

75 

50 

1-5 

\ 

:{2 

88 

40 

.'{•2 

i; 

: 

86 

:w 

95 

105 

:*r» 

.'{•7 

2 

45 

125 

25 

5 

3 

/, 

62 

ISO 

20 

9 

i 

i1.. 

68 

800 

20 

15 

/,. 

65 

420 

20 

21 

»; 

,*, 

70 

4JJ2 

IS 

24 

s 

80 

504 

18 

28 

!) 

95 

510 

17 

HO 

1  1 

100                      (120 

13 

48 

12 

125                     050 

13 

50 

.Most.  metals  oxidise  under  tin-  action  of  the  oxygen  in  the  atm< 
sphere,  as  is  insl;inc(-d  by  the  rusting  of  iron  exposed  to  the  ai 
This  is  a  fur  in  of  oxide  of  iron.  Upon  the  heating  of  the  iron,  th 
oxidation  is  very  much  more  rapid  and  intense.  Considerin 
(  he  method  of  cult  ing  by  a  jet  of  oxygen,  the  object  is  to  make  th 
oxidation  as  intense  as  possible,  so  as  to  burn  in  the  shortest  tim 
when  in  connection  with  the  oxygen,  and  to  obtain  the  narrower 
cut  possible.  The  oxidat  ion  takes  place  at  the  part  which  has  prc 
viously  been  heated  to  red  ness,  because  at  this  temperature  reactio 
takes  pla<c  readily.  Tim  combustion  of  this  part  of  the  iron  di,< 
engages  heat ,  a  portion  of  which  is  absorbed  by  the  neighbourin 
part.  This  is  sufficient  to  raise  it  to  a  red  heat,  so  that  it  in  tun 
burns,  and  this  reaction  is  progressively  propagated  throughou 
t  he  metal.  Tin-  oxide  formed  has  a  much  lower  melting-point  thai 
t  hat  of  the  metal,  and  is  detached,  leaving  the  iron  continually  bare 

Highly  carbonised  steels,  whose  melting-points  are  appreciabl; 
lower  than  that  of  iron  and  in  the  neighbourhood  of  the  oxide  of  th 
metal,  do  not  lend  themselves  to  cutting  because  the  oxidation  doe 
not  propagate  itself;  nor  does  cast  iron,  on  account  of  the  impossi 
bility  of  eliminating  the  oxide  mixed  with  the  molten  metal.  Iroi 
•  ind  steel  are  about-  the  only  metals  that  can  be  cut  by  the  oxy 


138  MODERN  METHODS  OF  WELDING 

acetylene  process.  This  is  owing  to  the  oxide  of  iron  and  steel 
melting  at  a  much  lower  temperature  than  the  metal  itself.  Other 
metals,  where  the  melting-point  of  the  oxides  and  the  metals  are 
nearly  equal  to  one  another,  cannot  be  cut  by  this  process.  The 
reason  why  iron  and  steel  can  be  cut  is  because,  when  the  metal  is 
heated  to  redness,  and  oxygen  impinges  upon  it,  it  is  immediately 
oxidised,  and  the  pressure  of  the  oxygen  blows  the  oxide  away  as  it  is 
formed,  leaving  a  clean  cut  through  the  metal.  Most  of  the  non- 
ferrous  metals  cannot  be  cut  by  oxygen  for  the  reason  stated  above, 
and  also  very  high  carbon  steels  do  not  lend  themselves  easily  to 
cutting.  They  can  be  cut,  but  it  is  very  difficult,  and  many  failures 
occur.  Nor  does  cast  iron  lend  itself  to  cutting  with  an  oxy-acetylene 
cutter. 

Cutting  by  a  jet  of  oxygen  can  only  be  applied  to  iron  and  steel 
in  a  continuous  manner  by  contact  with  oxygen,  for  the  reason 
that  iron  and  steel  oxidise  very  rapidly  when  heated  to  redness,  and 
the  oxide  of  iron  formed  by  the  impinging  of  the  jet  of  oxygen  com- 
bines and  forms  in  a  molten  mass  on  the  steel  or  iron  plate ;  and,  at 
the  same  time  that  the  molten  oxide  is  formed,  the  pressure  of  the 
oxygen  blows  the  molten  mass  away,  leaving  a  clear  channel  through 
the  whole  thickness  of  the  plate.  In  order  to  make  the  cut  continu- 
ous, it  is  necessary  to  maintain  the  steel  plate  at  a  red  heat  along  the 
line  of  cutting.  Taking  into  consideration  that  the  plate  absorbs 
a  quantity  of  the  heat  by  conducting  it  over  the  cold  parts  of  the 
plate,  the  cutting  pipe  has  to  have  a  preheating  flame,  in  addition  to 
the  jet  of  oxygen  for  blowing  away  the  oxide  as  it  is  formed. 
The  cutting  pipe  must  be  regulated  for  speed  by  the  heating 
of  the  plate,  and  this  heating  must  be  continued  as  the  cutting  pro- 
ceeds. It  is  not  necessary  to  heat  the  plates  to  more  than  red  heat 
if  a  clean  cut  is  desired.  By  raising  the  temperature  to  a  welding 
heat,  cutting  action  is  stopped,  and  the  metal  becomes  blobbed  and 
forms  a  clot  of  oxide  on  the  top  of  the  plate. 

One  must  try  to  reduce  the  oxygen  to  a  minimum  by  regulating 
the  supply.  It  is  not  necessary  to  have  high  pressure  or  a  large 
nozzle,  except  when  cutting  very  thick  stuff,  because  excess  of 
oxygen  means  that  the  oxide  will  contain  an  excess  of  oxygen  and 
the  resulting  oxide  will  be  Fe3O4 — i.e.,  three  of  iron  and  four  of 
oxygen.  If  the  oxygen  is  correctly  regulated  and  the  pressure  not 
too  heavy,  the  cutting  will  be  much  more  economical,  and  more 
lineal  feet  will  result,  with  cleaner  cuts.  The  oxide  formed  would 
be  FeO — i.e.,  one  of  iron  and  one  of  oxygen.  The  pressure  of  oxygen 
required  to  cut  the  various  thicknesses  must  be  carefully  considered. 


CUTTING  IRON  AND  STEEL  ];>/, 

In  many  cases  it  is  very  indeterminate.  What  is  desirable  is  the 
thinnest  possible  jet,  with  great  length,  capable  of  blowing  the  oxide 
away  as  it  is  formed,  leaving  the  narrowest  clean  cut,  and  using 
oxygen  at  the  very  lowest  pressure.  The  heating  flame— its  intend  v 
and  length,  the  distribution  of  heat— always  influences  the  result, 
and  its  direction  and  distance  are  most  important. 

Also,  the  purity  of  the  oxygen  is  most  important.  At  99  per 
cent,  purity,  the  maximum  lineal  feet  of  cutting  can  be  obtained; 
95  to  96  per  cent,  of  purity  reduces  the  lineal  cutting  from  10  to 
15  per  cent.  With  90  per  cent,  cutting  will  only  be  intermittent. 


FIG.  70.— THE  RADIOGRAPH  CUTTING  STEEL  PLATE  WITH  THE  OXY-  \<  i 
FLAME,  AT  SPEEDS  VARYING  FROM  18  INCHES  ^^^INCHES  PER  MIND 
PLATE  FROM  £  INCH  TO  20  INCHKS  THICK.        ^flb 

It  will  be  noted  that  practically  any  thic^HPcan  be  cut,  from  the 
thinnest  to  16  or  even  20  inches  thick,  mth  thick  plates  machines 
are  needed  to  guide  the  line  of  cutting.  Fig.  70  illustrates  cutting 
a  large  plate. 

Where  cutting  has  to  be  done  by  hand,  care  must  be  taken  that 
the  line  of  cutting  is  straight.  In  many  cases,  rollers  are  used  t«> 
steady  the  cutter  and  to  act  as  a  guiding  support.  Operator* 
must  see  that  the  heating  flame  and  the  delivery  of  the  oxjgert  for 
cutting  are  regulated  proportionally  to  the  thickness  of  the  plat*  t<> 
be  cut.  The  pressure  should  be  regulated  at  the  reducing  val\e. 
and  the  minimum  pressure  must  be  used  in  all  cutting  operations 
as  a  cleaner  cut  will  be  g9t.  If  a  high  pressure  of  oxygen  i 


140  MODERN  METHODS  OF  WELDING 

when  cutting  iron  or  steel,  it  spreads  around  the  place  where  heating 
is  taking  place;  hence  it  cools  the  surface,  thereby  retarding  the 
cutting. 

It  is  not  necessary  to  have  increased  pressure  of  oxygen.  Many 
welders  think  that  the  higher  the  oxygen  pressure,  the  quicker 
and  better.  This  is  a  fallacy.  Pressures  from  10  to  40  pounds  are 


FIG.  71. — COUPLED  CYLINDERS,  FOR  CONTINUOUS  WORK. 

ample  for  most  commercial  thicknesses,  and  more  cutting  and  neater 
work  will  be  obtained  if  the  oxygen  is  kept  at  these  pressures. 
Furtlor,  the  saving  in  oxygen  is  large— quite  20  per  cent.  It  is  not 
pressure  that  is  needed,  but  volume.  When  cutting  a  great  thick- 
ness, several  cylinders  are  brought  into  requisition  and  coupled  up 
together.  From  this  one  gets  a  large  volume;  but  it  only  needs  a 
medium  pressure.  The  above  illustration  shows  these  coupled  by 
cylinders. 


CUTTING  IRON  AND  STEEL  ]4i 

This  arrangement  enables  three  cylinders  at  a  time  to  be  de- 
tached  when  empty,  and  replaced  with  full  ones,  while  any  or  all 
of  the  others  are  feeding  oxygen  to  the  regulator  fixed  on  the  tripod 
stand  in  the  centre. 


Manufacturers  should  use  the  oxy-acetylrnr  cutting  process 
much  more  than  they  do  at  the  present  time.  They  will  find  impnr- 
tant  advantages  through  operating  the  torches  mechanically,  \\ln-n 
such  a  procedure  is  practicable.  More  notable  ainoni:  tin-  hnn'fits 
secured  from  mechanical  control  are  increased  prediction  from  the 


142 


MODERN  METHODS  OF  WELDING 


cutters  and  greater  uniformity  of  work.  Experience  is  required  to 
enable  the  hand  operator  of  a  cutter  to  produce  uniform  cuts.  In 
shops,  the  use  of  mechanically  operated  cutters  eliminates  the 
personal  equation  and  generally  improves  the  quality  of  the 
work. 

Figs.  72,  73.  and  74  are  remarkable  and  wonderful  machines. 
You  will  note  the  ease  with  which  the  cutter  is  handled,  also 
the  clean-cut  edge  which  it  leaves,  thereby  saving  machining. 


FIG.  73. — CIRCULAR  CUTS  IN  STEEL  PLATE  2 \  INCHES  THICK,  WITH  THE  RADIO- 
.     GRAPH,  AT  A  SPEED  OF  6  LlNEAL  INCHES  PER  MlNUTE. 

Inside  and  outside  diameters  of  these  flue  sheets  for  special  heaters  were  cut  with 
the  Radiograph  and  the  oxy -acetylene  torch. 

It  is  also  the  means  of  increasing  production,  as  cutters  are  moved 
at  the  correct  rate,  which  is  predetermined  by  the  feed  mechanism. 

Various  mechanically  operated  equipments  are  designed  for 
particular  requirements.  There  are  also  standard  designs  of  mechan- 
ical cutters  and  welding  blowpipes,  which  are  being  used  with  great 
success.  Provision  can  be  made  for  the  mechanical  control  of  cutters 
adapted  for  use  on  parts  of  a  variety  of  different  shapes. 

The  three  illustrations  show  that,  in  addition  to  making  straight 
cuts  on  flat  plates,  it  is  quite  feasible  for  cutters  to  follow  irregular 


CUTTING  IRON  AND  STEEL  143 

outlines  on  flat  plates,  or  to  make  cuts  on  cylindrically  shaped 
pieces. 

With  many  of  these  mechanical  equipments,  the  cutters  are 
guided  in  such  a  way  that  they  follow  the  line  upon  which  it  is 
desired  to  make  a  cut  without  calling  for  special  attention  from  the 
operator.     As  previously  mentioned,  the  provision  of  power  drive 
sets  the  pace  of  the  cutter,  so  that  it  is  fed  to  the  work  at  a  prede- 
termined speed  suitable  for  the  thickness  of  the  metal  that  is  being 
cut.     Figs.  72  and  73  show  two  mechanically  worked  cutters  for 
cutting  ragged  edges  for  such  pieces  as  boiler  heads,  which  have 
a   flange  drawn  up   around   the  circumference.     In  Fig.  72  the 
cutter  is  shown  trimming  the  flange  off  a  boiler  front  which  is  made 
of  steel  plate  1 J  inches  thick.     It  will  be  apparent  from  the  illus- 
tration that  the  cutter  is  supported  by  a  head  carried  on  a  radial 
arm,  on  a  machine  which  is  so  designed  that  the  cutter  head  can  be 
traversed  in  either  direction  on  the  radial  arm,  and  this  arm  can  be 
swung  round  the  column  of  the  machine.     This  combination  of 
movement  enables  the  cutter  to  be  fed  round  the  edge  of  cylindri- 
cally shaped  pieces,  as  shown.     The  cutter  head  is  furnished  with 
the  wheels,  which  engage  both  inside  and  outside  of  the  work  to 
provide  for  holding  the  point  of  the  cutter  in  proper  relation  to  the 
plate  it  is  cutting.     The  cutter  head  is  worked  by  the  electric  motor 
seen  above  the  radial  arm,  which  transmits  power  to  the  wheels  on 
the  head,  so  that  they  serve  the  double  purpose  of  holding  the  cutter 
in  the  proper  position,  and  feeding  it  over  the  work  at  the  proper 
rate.     The  plate  being  \\  inches  thick,  it  cuts  at  a  rate  of  1  foot  per 
minute,  and  leaves  a  sufficiently  good  finish,  so  that  no  subsequent 
machining  operation  is  required.     The  Radiograph  is  a  portable, 
motor-driven  machine,  combining  carriage  and  driving  mechanism 
with  motor  attached,  oxy-acetylene  or  oxy-hydrogen  cutting  torch, 
and  means  for  guiding  the  heating  or  cutting  gases  along  straight 
or  curved  lines,  at  constant  speed  adjusted  according  to  the  thick 
ness  of  the  plate  and  size  of  the  tip  used. 

In  making  motors  for  steam  turbines,  the  New  York  Shipbuilding 
Corporation  pour  the  molten  steel  into  the  mould,  which  is  made  8 
that  the  rotor  casting  stands  on  end,  makes  the  casting  longe 
which  acts  as  a  riser,  that  applies  pressure  and  assists  in  product 
of  a  solid  casting.     Obviously,  it  is  necessary  to  cut  off  this  surpli 
and  during  the  process  of  machining  this  steel  casting  i 
a  lathe.     Supported  in  this  way,  it  is  an  easy  matter  to  rotate 
casting  at  a  suitable  speed,  so  that  a  cutting  blowpipe  supportc 
the  proper  relation  to  the  work  will  have  the  steel  casting  f 
the  cutter,  at  the  proper  rate  for  making  this  cut. 


144 


MODERN  METHODS  OF  WELDING 


The  illustration  below  is  the  casting  described  herewith.  You  see 
that  it  is  in  the  lathe,  and  cut  through ;  the  blowpipe  is  fixed  over 
the  casting. 

This  rotor  casting  is  9  inches  thick  by  16  feet  6  inches  in  circum- 
ference, and  the  cut  was  completed  by  the  oxy-acetylene  cutter  in 
the  remarkably  short  time  of  thirty -five  and  a  half  minutes.  A 
good  idea  of  the  quality  of  the  finished  surface  left  by  the  cutter 
will  be  gathered  from  the  illustration. 


FIG.  74. — BODY  OF  STEAM  TURBINE  ROTOR  OF  CAST  STI:I;L. 

The  end  is  being  cut  off  by  rotating  it  in  the  lathe  to  feed  it  to  the  flame  of  the 
cutting  torch.     It  is  9  inches  thick. 

Users  of  cutting  and  welding  blowpipes  should  make  themselves 
familiar  with  the  properties  of  both  hydrogen  and  acetylene;  but 
there  are  some  who  have  not  had  occasion  to  investigate  the  proper- 
ties of  carbo-hydrogen.  This  gas  contains  from  85  to  88  per  cent, 
hydrogen,  and  15  to  12  per  cent,  of  light  hydrocarbons  of  the  higher 
heating  series.  It  is  claimed  that  less  oxygen  is  required  for  the 
combustion  of  this  gas  than  for  either  acetylene  or  hydrogen;  and 
the  temperature  of  the  carbo-hydrogen  flame  is  approximately 
4,800°F. 

In  referring  to  the  properties  of  combustible  gases  which  make 


CUTTING  IRON  AND  STEEL  145 

them  suitable  for  use  in  cutting  and  welding,  confusion  frequently 
arises  through  a  misconception  of  the  relation  which  exists  bet \v< •'  n 
the  number  of  heat  units  per  cubic  foot  of  gas  and  the  temperature 
which  can  be  developed  by  the  combustion  of  that  gas.  For  the 
performance  of  the  cutting  and  welding  operations,  the  number 
of  heat  units  per  cubic  foot  of  gas  is  a  matter  of  minor  importance 
in  determining  ability  to  give  efficient  service.  It  is  the  rapidity 
with  which  this  heat  is  liberated  to  develop  a  high  temperature  which 
determines  the  suitability  of  the  gas  for  use  in  the  blowpipe. 

The  fact  is  well  brought  out  by  comparing  the  heat  value  of  carbo- 
hydrogen  with  that  of  ordinary  illuminating  gas,  the  former  having 
approximately  480  British  thermal  units  of  heat  per  cubic  foot, 
while  the  latter  has  approximately  600  per  foot.  Despite  this 
fact,  illuminating  gas  is  unsuitable  for  use  in  a  blowpipe,  because, 
although  it  has  25  per  cent,  more  available  heat  per  unit  volume  of 
gas,  this  heat  is  not  liberated  rapidly  enough  to  generate  a  tempera- 
ture suitable  for  the  cutting  of  metals. 

It  is  claimed  by  the  Carbo-Hydrogen  Company  that  this  gas  has 
readily  cut  armour  plate  up  to  24  mches  thickness,  using  standard 
apparatus,  and  that  open-hearth  steel  pit  castings  36  inches  thick 
across  have  been  cut  in  half  by  a  special  apparatus,  using  carbo- 
hydrogen  as  the  combustible  gas.  For  this  work  a  number  of 
oxygen  cylinders  were  manifolded  together  and  a  preheating  flame 
was  used,  which  was  provided  by  a  blowpipe  fitted  with  a  J-inch 
gas  pipe,  taking  oxygen  from  the  manifold  supply  direct.  Of  course, 
this  was  an  unusual  operation,  and  the  cut  was  not  made  by  one 
continuous  traverse  of  the  cutter.  In  the  case  of  the  24-inch  armour 
plate  this  was  made  in  one  operation.  The  composition  of  the  carbo- 
hydrogen  gas  is  such  that  an  accurate,  clean  cut  is  made,  and  the  slag 
produced  is  almost  pure  oxide  of  iron,  there  being  very  little  pure 
iron  in  it.  This  indicates  that  the  cutting  is  accomplished  by  a 
complete  process  of  oxidation,  which  is  the  ideal  method,  and  not 
by  melting  the  iron.  Where  metal  is  severed  by  melting  it  is  almost 
inevitable  that  a  ragged  surface  should  be  left  in  making  a  cut,  so 
that  it  is  necessary  to  employ  some  subsequent  process  of  finishing 
before  the  work  is  ready  for  use. 

In  this  chapter  information  has  been  presented  concerning  miscel- 
laneous applications  which  have  been  made  of  mechanically  operated 
cutting  and  welding  blowpipes,  and  attention  has  been  called  to 
the  benefits  secured  through  the  substitution  of  mechanical  con- 
trol of  hand  operations.  Despite  the  increased  production  and 
higher  quality  of  the  workmanship  secured  through  mechanical 


10 


146 


MODERN  METHODS  OF  WELDING 


operations,  many  manufacturers  are  continuing  to  use  cutters  moved 
over  the  work  by  hand.  There  is  no  denying  that  the  latter  method 
is  capable  of  producing  highly  satisfactory  results  when  the  cutters 
are  placed  in  the  hands  of  skilled  operators ;  but  the  average  mechanic 
will  frequently  fail  to  produce  good  work  until  he  has  had  some  con- 
siderable amount  of  experience. 

It  is  well  worth  while  for  the  manufacturer  who  has  use  for  the 


FIG.  75. — FELLING  A  STACK  WITH  AN  OXYGEN  CUTTER. 

oxy-acetylene  torch  to  investigate  carefully  the  requirements  of  his 
work,  with  the  idea  of  determining  whether  it  could  not  be  handled 
by  one  of  the  standard  cutting  or  welding  machines. 

If  investigation  shows  that  the  work  could  not  be  handled  on  any 
of  the  available  commercial  equipments,  the  next  step  is  to  ascertain 
whether  a  special  machine  using  standard  cutters  could' not  be  deve- 
loped at  a  reasonable  expense.  If  so,  development  of  such  an  equip- 
ment will  usually  prove  a  highly  profitable  investment,  both  from 


CUTTING  IRON  AND  STEEL 


147 


the  standpoint  of  direct  earnings  and  also  by  making  an  improve- 
ment in  the  quality  of  workmanship  where  cutting  or  welding  opera- 
tions have  to  be  performed. 


Fig.  75  shows  an  unique  application  of  the  onttinc  Mmv|'i|M-.  th«- 
stack  cut  through  at  the  bottom  at  an  angle  to  set.  the  I 

Remarkable  results,  which  have  revolution.., I  many  method*  of 


148  MODERN  METHODS  OF  WELDING 

steel  cutting,  are  being  obtained  with  motor-driven  machines. 
One  such  machine  is  sold  under  the  name  of  "  oxygraph."  By 
following  a  drawing  with  a  motor-driven  tracer,  steel  to  the  thickness 
of  several  inches  is  cut  out  accurately  in  intricate  forms.  The 
motor  is  very  small  and  compact  and  requires  very  little  power. 
It  can  be  driven  either  by  battery  or  by  wire  attached  to  an  electric- 
light  fixture.  Being  motor-driven  it  moves  with  a  uniform  speed, 
and  corners  and  curves  are  cut  with  great  exactness. 

It  will  cut  steel  plate  from  1  to  15  inches  or  more  in  thickness, 
it  cuts  with  a  narrow  smooth  kerf,  along  straight  lines,  sharp 
angles,  or  curves,  according  to  the  drawing  or  pattern.  The  panta- 


FIG.  77. — TRACER  WHEEL,  SWIVEL  STANDARD,  RHEOSTAT  AND  ELECTRIC  MOTOR 
WITH  SPEED  CONTROLLER  or  No.  IA  OXYGRAPH. 

graph  principle  is  employed  with  a  motor-propelled  tracing  wheel, 
with  which  the  lines  of  the  drawing  are  followed  and  reproduced  with 
the  cutting  torch.  The  only  power  required  is  for  revolving  the 
tracing  wheel,  and  this  is  supplied  by  a  small  motor  attached  to  the 
tracing  head,  which  may  be  connected  to  the  ordinary  electric  light 
or  power  circuit.  The  speed  of  the  cutting  varies  from  2  to  18  inches 
per  minute. 

Machine  torches  of  great  power  have  been  developed  for  oxy- 
acetylene  and  oxy-hydrogen  cutting  with  the  oxygraph  that  operate 
successfully  on  the  heaviest  work.  The  adjustment  of  the  cutting 
flame  is  easily  learned  and  skill  in  the  operation  of  the  machine 


CUTTING  IRON  AND  STEEL 


149 


is  soon  acquired  by  inexperienced  operators.  An  operator  capable 
of  running  a  drilling  machine  should  be  able  to  work  the  oxygraph 
efficiently  after  a  few  days'  instruction. 

The  oxygraph  has  wide  application  and  many  uses  in  tool  shops, 
manufacturing  plants,  locomotive  works,  shipyards,  drop-forging 
concerns,  and  wherever  tools,  dies,  forgings,  and  shapes  are  prodiu •<•<! . 
The  cutting  action  of  the  torch  flame  is  smooth  and  rapid,  and  as  any 


FIG    78 -MACHINE  CUTTING  TORCH  WITH  MOTOR  CONTROL  SWITCH,  AND  I 
AND-PINION  VERTICAL  ADJUSTMENT. 

shape  can  be  cut  it  is  comparable  to  a  metal  bandsaw  of  great  power 
capable  of  cutting  steel  15  inches  thick  at  the  rate  of  4  or  5 
per  minute,  following  straight  lines,  curves,  and  angles,  acute 
obtuse.     Thin  sections  are  cut  more  rapidly,  of  coure 

Punches,  dies,  stripper  plates,  and  bolsters  are  cut  m  tool 
with  the  oxygraph  with  resultant  saving  of  time  and  cost 
to  500  per  cent.,  and  even  more,  saving  in  some  case 


150  MODERN  METHODS  OF  WELDING 

The  usual  practice  in  making  a  cutting  or  trimming  die  is  to  plane 
the  block  on  the  top  and  bottom,  bevel  the  sides,  lay  out  and  drill 
holes  to  the  line,  cut  out  the  walls  between  the  drilled  holes  with  a 


FIG.  79. — SMALL  SOLID  END  CONNECTING-ROD  AND  BILLET  FROM  WHICH  IT  WAS 

CUT    ON   THE   NO.    lA   OXYGEAPH. 

broach  or  drift,  and  finish  with  a  hammer,  chisel,  and  file,  or  by  back- 
ing out  on  a  shaper  or  slotter.  Almost  invariably  a  die  made  in  this 
manner  warps  and  twists  in  the  process,  and  requires  either  re- 


FIG.  80. — LEATHER-CUTTING  PUNCH  FOR  SHOE  MANUFACTURE  AND  TOOL  STEEL 

PIECE   FROM   WHICH   IT   WAS   CUT. 

planing  on  the  bottom  or  shimming  up  in  the  bolster.  The  removal 
of  the  mass  of  steel  in  the  centre  of  the  die  relieves  internal  stress 
and  lets  the  block  warp  out  of  shape.  Not  so  when  the  rough  die 
block  is  cut  out  with  the  oxygraph.  All  troubles  of  this  sort  are 


CUTTING  IRON  AND  STEEL  151 

eliminated  and  the  danger  of  cracking  in  hardening  is  reduced  to  a 
minimum.  The  rough  die  block  is  preheated  and  cut  before  planing, 
using  a  paper  drawing  to  guide  the  tracer  wheel.  When  the  open- 
ing has  been  cut,  the  die,  still  hot,  is  placed  in  an  annealing  box, 
covered,  and  left  to  cool.  When  cold  it  is  planed  and  finished  in  the 
usual  manner  with  the  assurance  that  internal  strains  have  been 
relieved.  Finishing  the  die  to  precise  dimensions  and  backing  out 
for  clearance  is  done  in  the  usual  manner. 

Not  only  is  the  oxygraph  useful  for  blocking  out  dies  but  it  may 
be  used  also  to  cut  the  stripper  plates  and  bolsters.  The  use  of  the 
No.  IA  oxygraph  in  a  tool  shop  outlined  in  the  foregoing  is  one  of 
the  many  that  can  be  made  in  the  manufacturing  plant.  It  may  be 


FIG  81  -DROP  FORGED  WRENCH  TRIMMING  DIE  ROUGHED  OUT  ON  No.  IA  (to- 

GRAPH    AND   READY   TO    BE   "  BACKED    OUT. 

used  for  cutting  metal  templates,  cams,  patterns    risers  for  fire 
escapes,  and  all  shape  cutting  of  any  description  which  comes  wit 
the  range  and  capacity  of  the  machine. 

The  No.  2  oxygraph  is  designed  for  such  work  as  cutting  the  . 


sho,  a  fe,v  sables  of  ,  hat  ta 
with  these  wonderful  small  machines;  those  shown  , 

°Th?above  and  other  illustrations  follo.-ing  wffl  -  -    to  give 


152 


MODERN  METHODS  OF  WELDING 


some  range  of  work  and  the  speed  of  performance.     But  no  matter 
what  the  shape  is,  provided  the  metal  is  steel  or  wrought  iron 


No. 


No.  1 


No.  2 


No.  3 


No.  1 


No.  2 


No.  3 


FIG.  82. — VIEWS  or  THREE  SETS  or  DIES  CUT  FROM  110-PoiNT  CARBON  STEEL, 
2£  INCHES  THICK,  ON  No.  1  OXYGRAPH. 

which  may  be  forged  to  shape,  it  doubtless  can  be  advantageously 
cut  in  the  process  of  fabrication  to  reduce  forging  and  machining 
cost.  Forge  shops  use  the  oxygraph  to  increase  the  productive 


CUTTING  IRON  AND  STEEL  ir,3 

capacity  of  their  forging  hammers  and  presses.  For  instance,  a 
billet  weighing  many  tons  may  be  forged  to  a  roughly  rectangular 
shape,  and  from  that  be  cut  in  two,  three,  or  four  crank-cheeks 
weighing,  perhaps,  2  tons  each.  The  resultant  scrap,  in  some  cases, 
is  of  a  shape  that  can  be  utilised  for  smaller  work  by  being  reforged, 
hence  saving  not  only  time  in  forging  and  machining,  but  metal  as 
well.  Cutting  may  be  started  at  the  edge  or  within  the  edge  of  a 
piece,  if  conditions  require  it.  The  oxygraph  torch  flame  quickly 
perforates,  and  thus  the  cost  of  drilling  and  handling  is  saved.  The 
edges  of  the  cut  pieces  are  square  and  smooth  and,  in  many  cases, 
no  machining  is  required  for  finish.  If  extreme  accuracy  is  required, 
the  cutting  can  be  done  so  close  to  the  line  that  machining  is  a  light 
finishing  operation  only.  These  cutting  machines  are  manufactured 
in  America  by  Davis-Bournonville  Company. 
The  following  are  the  costs : 


No. 

Time. 
Minutes. 

Oxygen. 
Cubic  Feet. 

Acetylene. 
Cubic  Feet. 

Length 
of  Cut. 
Inches. 

Gas  Cost 
at  Id.  (.'uliic 
Foot. 
Pence. 

1 

3-5 

10-5 

1-2 

30 

IS 

0 

4-0 

13-2 

1-4 

34 

17 

3 

4-0 

13-2 

1-4 

34 

17 

11-5 

36-9 

4-0 

1 

98 

49 

CHAPTER  XXIV 
THERMIT  WELDING 

Thermit  Process. — This  process  of  welding  metals  is  effected  by 
pouring  superheated  thermit  steel  around  the  parts  to  be  united. 
Thermit  is  a  mixture  of  finely  divided  aluminium  and  oxide.  This 
mixture  is  placed  in  a  crucible,  and  the  steel  is  produced  by  igniting 
the  thermit  in  one  spot  by  means  of  a  special  powder,  which  gener- 
ates the  intense  heat  necessary  to  start  the  chemical  reaction.  When 
the  reaction  is  once  started  it  continues  throughout  the  whole  mass, 
the  oxygen  of  the  iron  being  taken  up  by  the  aluminium  (which  Las 
a  strong  affinity  for  it),  producing  aluminium  oxide  (or  slag)  and 


FIG.  83. — THE  ABOVE  is  A  THERMIT  WELD,  IN  WHICH  NEW  TEETH  HAVE  BEEN 

WELDED  IN. 

superheated  thermit  steel.  Ordinarily,  the  reaction  requires  from 
thirty-five  seconds  to  one  minute,  depending  upon  the  amount  of 
thermit  used.  ,As  soon  as  it  ceases,  the  steel  sinks  to  the  bottom 
of  the  crucible,  and  is  tapped  into  a  mould  surrounding  the  parts  to 
be  welded.  As  the  temperature  of  the  steel  is  about  5,400°  F.  it 
fuses  and  amalgamates  with  the  broken  sections,  thus  forming  a 
homogeneous  weld. 

It  is  necessary  to  preheat  the  sections  to  be  welded  before  pour- 
ing to  prevent  the  chilling  of  the  steel.  The  principal  steps  of  the 
operation  are :  to  clean  the  sections  to  be  welded ;  to  remove  enough 
metal  at  the  fracture  to  provide  for  a  free  flow  of  thermit  steel;  to 
align  the  broken  members  and  surround  them  with  a  mould  to  retain 

154 


THERMIT  WELDING  155 

the  steel ;  to  preheat  by  a  torch  or  other  suitable  heater  to  prevent 
chilling  the  steel;  to  ignite  the  thermit  and  tap  the  molten  steel 
into  the  mould. 

This  process  is  specially  applicable  to  the  welding  of  large  sections. 
It  has  been  extensively  used  for  welding  locomotive  frames,  broken 
motor  castings,  rudders  and  sternposts  of  ships,  crankshafts,  spokes 
of  driving  wheels,  connecting-rods,  and  heavy  repair  work  in  general. 
One  great  advantage  of  the  thermit  process  is  that  broken  parts  can 
usually  be  welded  in  place.  For  example,  locomotive  frames  are 
welded  by  simply  removing  parts  that  would  interfere  with  the  appli- 
cation of  a  suitable  mould.  Thermit  is  also  used  for  pipe  welding 
and  in  foundry  practice  to  prevent  the  "  piping  "  of  ingots. 


FIG.  84. — THERMIT- WELDED  CROSSHEAD. 

Preparation. — The  first  step  in  the  operation  of  thermit  welding 
is  to  clean  the  fractured  parts  and  cut  away  enough  metal  to  ensure 
an  unobstructed  flow  of  the  molten  thermit.  The  oxy-acetylene 
cutting  blowpipe  is  very  efficient  for  this  operation.  The  amount 
that  should  be  cut  away  depends  upon  the  size  of  the  work.  Assum- 
ing that  a  locomotive  frame  is  to  be  welded,  the  space  should  be 
about  f  inch  wide  for  a  small  frame,  and  1  inch  wide  for  a  large 
frame.  The  frame  sections  are  then  jacked  apart  about  f  inch  to 
allow  for  contraction  of  the  weld  when  cooling.  Trammel  marks 
are  scribed  on  each  side  of  the  fracture  to  show  the  normal  length. 
If  the  weld  is  to  be  made  on  one  member  of  a  double-bar  frame, 
the  other  parallel  member  should  be  heated  with  a  blowpipe  to 
equalise  the  expansion  in  both  sections  and  prevent  unequal 
strains. 

Fig.  84  shows  a  Thermit-Welded  Crosshead,  which  was  broken 


156  MODERN  METHODS  OF  WELDING 

through  the  middle  before  welding  took  place.  The  two  pieces  of  the 
crosshead,  before  welding,  are  bevelled  on  each  edge  of  the  fracture, 
so  as  to  give  a  further  area  of  thermit,  thereby  getting  greater 
strength  in  the  weld.  The  bevelling  was  done  with  an  oxy-acetylene 
cutter,  using  acetylene  and  oxygen. 

Mould  for  Thermit  Welding. — The  mould  surrounding  the  frac- 
tured part  should  be  so  arranged  that  the  molten  thermit  will  run 
through  the  gate  to  the  lowest  part  of  the  mould  and  rise  through 
and  around  the  parts  to  be  welded.  The  thermit  steel  is  poured 
through  the  gate  and  forms  a  riser  which  rises  into  a  space  after 
passing  round  and  between  the  ends  of  the  fractured  crosshead. 
The  thickest  part  is  directly  over  the  fracture,  and  the  band  overlaps 
the  edges  of  the  fracture  by  at  least  one  inch.  An  opening  is  also 
made  for  preheating  the  ends  to  be  welded. 

Patterns  for  the  riser,  pourings,  and  heating  gates  can  be  made 
of  wood.  The  riser  should  be  quite  large  enough,  because  the  steel 
that  first  enters  the  mould  is  chilled  somewhat  by  coming  in  con- 
tact with  the  metal  even  when  preheated.  This  chilling  effect  is 
overcome  by  using  enough  thermit  steel  to  force  the  chilled  portion 
into  the  riser  and  replacing  it  by  metal  which  has  practically  the 
full  temperature  received  during  reaction.  When  the  mould  and 
the  box  are  filled  and  tamped,  the  wooden  runner  and  riser  patterns 
are  withdrawn.  The  mould  is  then  ready  for  the  preheating  and 
the  drying  operation,  which  causes  the  wax  matrix  to  melt  and  run 
out.  The  mould  must  be  made  of  some  refractory  material,  owing 
to  the  intense  heat. 

Thermit  welding  was  first  introduced  in  1903  and  was  adopted 

on  marine  work,  which  has  had  a  great  many  successful  welds  of  this 

/  nature.     It  is  being  used  largely  by  railway  and  tramway  companies. 

One  can,  nearly  always,  see  the  process  being  worked  in  the  streets 

\  on  the  tramway  lines. 

-  There  are  many  technical  schools  in  every  large  city,  where  in- 
struction and  practice  are  given  in  thermit  welding,  as  well  as  other 
welding  processes. 

Thermit  Required  for  Welding. — The  quantity  of  thermit  re- 
quired for  making  a  weld  can  be  determined  from  the  cubic  content 
of  the  weld.  Calculate  the  contents  of  the  weld  and  its  reinforce- 
ment in  cubic  inches,  double  this  amount  to  allow  for  filling  the  gate 
and  riser,  and  multiply  by  0-56  to  get  the  number  of  pounds  of 
thermit  required.  When  wax  is  used  for  filling,  the  weight  of  the 
thermit  can  be  determined  as  follows :  Weigh  the  wax  supply  before 
and  after  filling  the  fracture.  The  difference  in  weight  (in  pounds)  of 


THERMIT  WELDING  157 

the  quantity  used  multiplied  by  22  will  give  the  weight  of  thermit 
in  pounds. 

When  a  quantity  of  more  than  10  pounds  of  thermit  is  to  be  need, 
add  10  per  cent,  of  steel  punchings  (not  over  J  inch  diameter),  or 
steel  scrap,  free  from  grease,  to  the  thermit  powder.  If  the  thermit 
exceeds  50  pounds,  15  per  cent,  of  small  mild  steel  rivets  may  be 
mixed  with  it.  One  per  cent,  by  weight  of  pure  manganese  and 
1  per  cent,  of  nickel  thermit  should  be  added  to  increase  the  strength 
of  the  thermit  steel. 

Preheating — Making  a  Weld. — The  ends  to  be  welded  should  be 
red-hot  at  the  moment  the  thermit  steel  is  tapped  into  the  mould. 
This  preheating  is  done  preferably  by  a  gasolene  compressed  air 
burner.  As  previously  mentioned,  it  melts  the  wax  matrix  used  for 
filling  the  fractures  to  form  the  pattern  for  the  reinforcing  band. 
When  the  ends  have  been  heated  red,  quickly  remove  the  burner  and 
plug  the  preheating  hole  with  a  dry  sand  core,  backing  it  up  with  a 
few  shovelfuls  of  sand,  well  packed.  The  end  of  the  cone-shaped 
crucible  should  be  directly  over  the  pouring  gate  and  not  more  than 
4  inches  above  it.  To  start  reaction,  place  j  teaspoonful  of  ignition 
powder  on  the  top  of  the  thermit  and  ignite  with  a  storm -match. 
It  is  important  that  sufficient  time  be  allowed  for  the  completion  of 
the  thermit  reaction  and  for  the  fusion  of  the  steel  punchings  which 
have  been  mixed  with  the  thermit. 

With  charges  containing  from  30  to  40  pounds  of  thermit,  the 
crucible  should  not  be  tapped  in  less  than  thirty-five  seconds; 
with  charges  containing  50  to  75  pounds,  forty  seconds;  75  to  100 
pounds,  fifty  seconds  to  one  minute.  When  welding  a  broken 
frame,  as  shown  previously,  the  screw  jack  used  for  forcing  apart 
should  be  turned  back  somewhat  to  relieve  the  pressure  gradually 
as  the  weld  cools.  After  pouring  the  mould  should  remain  in  place 
as  long  as  possible  (preferably  ten  to  twelve  hours)  to  anneal  the 
steel  in  the  weld;  and,  in  any  case,  it  should  not  be  disturbed  at 
least  two  hours  after  pouring.  When  welding  a  broken  spoke  in  a 
driving  wheel  or  a  similar  part,  it  is  necessary  to  preheat  the  adjaeen  t 
spokes  in  order  to  prevent  undue  strains  through  expansion  and 
contraction.  If  a  section  of  a  spoke  is  broken  out,  it  can  be  cast  in, 
but  if  the  space  is  over  6  inches  long  it  is  better  to  insert  a  pi. 
steel  and  make  a  weld  at  each  end.  Owing  to  the  high  temperature 
(5,400°  F.),  and  the  violent  ebullition  of  thermit  during  reaction. 
the  crucible  must  be  relined  with  a  very  refractory  material.  The 
crucibles  used  for  this  purpose  have  sheet-iron  shell  and  are  lined 
with  magnesia. 


158       „          MODERN  METHODS  OF  WELDING 

Filling  Shrinkage  Holes  and  Surface  Flaws. — The  filling  of  surface 
flaws  in  castings  and  forgings  usually  requires  from  2  to  10  pounds  of 
thermit. 

To  make  a  weld  of  this  kind,  place  an  open  mould  around  the 
part  to  be  filled  large  enough  to  overlap  it  about  J  inch ;  clean  the 
hole  thoroughly  and  heat  to  red-heat  by  means  of  a  strong  blow- 
burner.  Use  18  ounces  of  thermit  for  each  cubic  inch  of  space, 


FIG.  85. — THERMIT- WELDED  ROCK  CRUSHER. 

but  not  less  than  2  pounds  for  any  one  weld.  Place  a  small  amount 
of  thermit  in  the  crucible,  which,  in  this  case,  is  of  a  small  size  for 
hand  use.  Ignite  the  thermit  with  the  ignition  powder,  and  as 
soon  as  it  begins  to  turn  add  the  remainder,  feeding  it  fast  enough 
to  keep  the  combustion  going.  When  the  reaction  is  completed 
quickly  pour  the  slag  (which  is  about  three-fourths  of  the  liquid) 
into  dry  sand.  Then  pour  the  steel  into  the  open  mould  and  sprinkle 


THERMIT  WELDING  ir>n 

loose  thermit  on  the  top  to  prolong  the  reaction,  as  the  casting,  even 
when  preheated,  will  have  a  chilling  effect  on  the  steel. 

Composition  of  Thermit  Steel. — An  average  analysis  of  thermit 
steel  is  as  follows:  Carbon,  0-05  to  0-10;  manganese,  0-08  to  O-lO; 
silicon,  0-04  to  0-05;  aluminium,  0-07  to  0-18  per  cent.  The  tensile 
strength  is  about  65,000  pounds  per  square  inch. 

Fig.  85  is  a  remarkable  weld  of  a  rock  crusher  for  the  Casparis 
Stone  Company.  The  eccentric  bearing  broke  off,  leaving  a 
fractured  surface  extending  longitudinally  through  the  bearing, 
measuring  6  feet  2  inches  long  and  an  average  of  about  7  inches 
thick.  A  mechanical  repair  was  first  attempted  on  the  new  brake, 
which,  however,  failed  only  after  a  few  days'  service.  Resort  was 
then  made  to  the  thermit  process,  and  the  casting  was  shipped 
to  the  thermit  factory.  The  broken  sections  were  lined  up,  a  gap 
of  about  3  inches  between  the  sections  was  cut  out  with  the  oxy- 
acetylene  flame,  90  pounds  of  wax  applied  in  the  welding  gap,  and 
a  mould  box  built  round  the  fracture.  Six  preheating  gates  were 
made  in  the  mould.  The  preheating  was  begun  at  4  a.m.  on  the  day 
of  the  pour ;  1 J  hours  of  preheating  were  required  to  burn  all  the 
wax  out  of  the  mould.  The  preheating  was  kept  up  for  about  twelve 
hours  until  3.45  p.m.,  the  time  the  reaction  started.  The  weld  is 
illustrated  on  p.  158. 

Particular  interest  attaches  to  this  repair  because  an  extra  large 
crucible,  having  a  capacity  of  2,000  pounds  of  thermit,  and  of  some- 
what different  design  from  the  standard  crucible,  was  used  experi- 
mentally. The  crucible  was  filled  almost  to  its  2,000  pounds 
capacity,  1,750  pounds  of  railroad  thermit  being  used.  In  spite  of 
the  enormous  amount  of  thermit  formed  in  one  crucible,  the  re- 
action and  pour  were  accomplished  with  entire  success.  The  crucikkp 
rested  steadily  and  motionless  on  its  four  supports  throughout 
reaction.  Sixty  seconds  were  allowed  for  the  reaction  to  take  place, 
after  which  the  crucible  was  tapped  in  the  usual  manner,  in  the  case 
of  large  welds  by  means  of  a  long  iron  rod.  From  the  moment  of 
tapping  it  took  two  and  three-quarter  minutes  for  the  contents  to 
run  out,  as  compared  with  the  one  minute  generally  re<|iiire<l  in  t he- 
case  of  number  10  crucible.  The  illustration  is  self-ex planat. 
It  shows  the  arrangement  of  the  gates  and  riser,  and  indicates  the 
excess  of  metal  present  after  the  mould  box  was  finally  removed. 


CHAPTER  XXV 

PROPERTIES  OF  PRINCIPAL  NON-FERROUS  METALS 

SCATTERED  throughout  the  pages  of  technical  literature  are  various 
references  to  non-ferrous  metals  and  alloys,  the  importance  of  which 
is  apt  to  be  lost  sight  of  because  they  become  inaccessible  after  a 
short  time.  It  is  therefore  desirable  that  such  information  should  be 
carefully  sifted  and  what  is  useful  in  it  collated  and  presented  in  a 
handy  form.  Such  is  the  purport  of  the  present  chapter. 

The  science  of  metallurgy  has  developed  wonderfully  within  the 
last  few  years,  especially  with  regard  to  the  non-ferrous  metals. 
Manufacturers  are  awakening  to  the  fact  that  many  of  the  disturbing 
influences  which  mar  their  best  efforts  are  due  to  prevalent  miscon- 
ceptions respecting  the  combined  chemical  compositions  and  the 
physical  structures  of  the  materials,  and  that  henceforward  science 
and  practice  must  go  hand  in  hand  if  true  progress  is  to  be  attained. 

An  ordinary  chemical  analysis,  supplemented  by  the  usual 
physical  tests,  was,  at  one  time,  considered  to  give  the  total  history 
of  an  alloy.  Things  have  changed,  however,  and  it  is  now  recognised 
that  metals  and  compounds  may  be  incorporated  in  an  alloy  under 
conditions  which  would  so  change  the  arrangements  of  the  con- 
stituents as  to  render  it  difficult,  if  not  impossible,  to  determine 
the  original  state  of  combination  or  the  ultimate  condition  of  the 
product.  There  has  been  no  lack  of  fanciful  theories  in  regard  to 
the  segregation,  crystallisation,  and  fatigue  of  metals,  some  of 
them  based  on  insufficient  data  derived  from  purely  physical 
and  chemical  tests. 

A  new  branch  of  metallurgical  study  has  recently  come  into 
prominence  under  the  name  of  "metallography  " — that  is,  the  micro- 
scopical examination  of  the  structure  of  metals,  which  has  already 
been  the  means  of  revealing  the  causes  of  many  peculiarities  of  metals 
and  their  alloys  and  confirming  other  theories  concerning  them 
which  used  to  be  looked  upon  as  parabolic.  One  of  the  most  im- 
portant properties  or  changes  which  occur  in  alloys  is  that  of  liquida- 
tion, which  was  only  proved  by  metallographic  examination. 

When  a  solution  fluid  at  ordinary  temperature  is  allowed  to  cool 

160 


PROPERTIES  OF  PRINCIPAL  NON-FERROUS  METALS     161 

below  its  congealing-point,  the  process  frequently  takes  place  in  such 
a  manner  that,  as  cooling  progresses,  certain  constituents  of  the 
solution  congeal  first,  whilst  the  solution  still  remaining  liquid  under- 
goes constant  changes  in  composition  until  a  certain  point  is  reached, 
after  which  this  solution  also  congeals.  The  solution  congealing  last 
is  called  the  eutectic  (most  fluid)  solution.  On  examination  of  the 
latter,  it  will  be  found  that  during  cooling  a  disintegration  of  the 
constituents  previously  dissolved  in  one  and  another  has  taken  place, 
and  that  the  solution  now  forms  only  an  intimate  mixture  of  these 
constituents. 

Many  alloys  show  a  similar  behaviour  when  cooling.  If,  for 
instance,  a  melted  zinc-copper  alloy  containing  more  than  72  per 
cent,  of  zinc  be  allowed  to  cool,  zinc  crystals  are  first  separated, 
while  an  alloy  poorer  in  zinc  still  remains  liquid.  This  separation 
of  zinc  is  continued  until  the  content  of  the  zinc  has  been  reduced 
to  72  per  cent.,  which  takes  place  when  the  temperature  has  fallen 
to  1,404°  F.  This  is  the  eutectic  point:  a  eutectic  alloy  which  no 
longer  separates  any  constituents  but  solidifies  throughout  at  that 
temperature  consists,  therefore,  of  72  parts  of  zinc  and  28  parts  of 
copper.  In  congealing  it  disintegrates,  however,  to  an  intimate 
mixture  of  its  constituents  which,  on  reheating,  first  dissolve  again 
in  one  another,  and  with  an  increase  of  temperature  gradually  dis- 
solve the  previously  separated  zinc.  If,  on  the  other  hand,  the  alloy 
contains  less  than  72  per  cent,  of  zinc  and  more  than  28  per  cent, 
of  copper,  copper  is,  in  congealing,  first  separated  till,  at  1,404°  F., 
the  composition  of  the  eutectic  alloy  has  again  been  reached  and 
then  also  congeals. 

Specific  Gravitij.—The  specific  gravity  or  density  of  alloys  corre- 
sponds only  in  a  few  cases  with  that  which  would  result  by  calcula- 
tion from  the  specific  gravities  of  the  constituents.     The  specific 
gravity  should  be  calculated  from  the  volumes  and  not  from  the 
weights.     Dr.  Ure  gives  the  correct  rule  as  follows :  Multiply  the  sum 
of  the  weight  into  the  products  of  the  two  specific  gravity  numbers 
for  a  numerator  and  multiply  each  specific  gravity  number  into  the 
weight  of  the  other  body,  and  add  the  products  for  a  denominator. 
The  quotient  obtained  by  dividing  the  said  numerator  by 
denominator  is  the  computed  mean  specific  gravity  of 
With  regard  to  the  influences  exerted  upon  the  strength  of 
'  by  alloying,  the  following  general  law  may  be  laid  down.     By  t 
absorption  of  a  foreign  body  the  strength  of  the  metal  is  mcr 
It  grows  with  the  content  of  the  foreign  body  until  the 
reached  a  certain  proportion,  which  varies  in  individual  ca 


162 


MODERN  METHODS  OF  WELDING 


When  this  limit  has  been  passed,  the  strength  again  decreases,  fre- 
quently with  great  rapidity,  provided  that  the  body  itself  does  not 
possess  greater  strength  than  the  metal.  By  the  addition  of  a  third 
metal  to  an  alloy  consisting  of  two  metals,  it  is  sometimes  possible 
to  bring  about  an  additional  increase  in  strength. 

Limit  of  Elasticity. — In  alloying  a  metal  the  limit  of  elasticity 
increases  steadily  with  the  breaking  strength,  limit  of  elasticity,  and 
breaking  weight  moving  more  closely  together.  The  limit  of  elasti- 
city usually  increases  still  further  when,  with  the  increase  of  the 
foreign  body  added,  the  highest  degree  of  strength  has  already  been 
attained,  and  a  decrease  in  strength  reappears.  Limit  of  elasticity 
and  strength  sometimes  finally  converge. 

MIXTURES  OF  ALLOYS. 


Copper. 

Tin. 

Zinc. 

Bell-metal   .  . 

78 

22 



Standard  bell-metal 

Gun-metal  .  . 

90 

10 

— 

Ordnance  castings 

Gun-metal  .  . 

88 

10 

— 

Steam  chest  pumps 

Gun-metal  .  . 

86 

14 

— 

Hard  bearing  metal 

Naval  brass 

62 

j 

37 

Stanchions,  tube  plates 

Sheet  brass  .  . 

70 

— 

30 

For  sheet  tubes 

Ordinary  brass 

66f 

— 

33i 

General  use 

Manganese  bronze 

56 

0-9 

41 

Gun-  metal  ord. 

88 

8 

2 

General  use 

Yellow  brass 

85 

3 

15 

General  plumbing  work 

Iron. 

Phosphor-bronze    . 

• 

89-5 

10 

0-5 

Heavy  bearings 

MELTING  AND  BOILING  POINTS  OF  METALS. 


Melting-Points. 
Degrees  C. 

Boiling  -Points. 
Degrees  C. 

Aluminium 

658-7 

1,800 

Copper 

1,803 

2,310 

Iron 

1,520 

2,450 

Tin 

231-9 

2,270 

Zinc 

419-4 

905-7 

Gun-metal 

995 

1,825 

Red  brass 

970 

1,780 

Low-grade  brass 

980 

1,795 

Bronze  with  zinc 

980 

1,795 

Cast  yellow  brass 

895 

1,645 

Naval  brass 

855 

1,520 

Manganese  bronze 

870 

1,600 

PROPERTIES  OF  PRINCIPAL  NON-FERROUS  METALS    163 

The  purest  metals  possess  the  greatest  flexibility.  By  alloying 
this  property  is  diminished,  and  sometimes  almost  reduced  to 
nothing.  The  melting  temperature  of  metals  is  frequently  lo\v<  r<  d 
by  alloying.  Therefore  it  is  essential  that,  when  welding  takes  place 
upon  non-ferrous  metals,  precautions  must  be  taken  not  to  add 
impure  metals  from  the  welding -rod  into  the  welded  portion. 
Also  it  is  important  that  the  metal  article  being  welded  and  the 
welding-rod  shall  be  one  and  the  same  material,  plus  ingredients  to 
replace  the  element  that  is  volatilised  during  welding. 


CHAPTER  XXVI 
DELTA  METALS 

THE  alloys  known  under  the  name  of  "  delta  metals  "  are  a  series 
of  high-class  engineering  alloys,  of  which  the  first  was  placed  on 
the  market  in  1885  by  the  eminent  metallurgist,  the  late  Alexander 
Dick.  These  metals  have  been  greatly  developed  and  comprise  a 
whole  group  of  different  alloys.  Hence  there  are  naturally  always 
welding  repairs  in  these  metals  to  be  done.  A  description  of  their 
properties  will  enable  the  student  to  distinguish  them  from  other 
metals  and  alloys,  so  that  the  treatment  may  be  administered  as 
required. 

It  is  obviously  impossible  to  combine  in  one  single  alloy  all  the 
physical  and  chemical  properties  suited  to  a  great  variety  of  pur- 
poses. The  different  standard  alloys  vary  in  composition  accord- 
ing to  the  purposes  for  which  they  are  more  particularly  adapted. 

Some  alloys  possess  in  every  degree  the  properties  of  malleability, 
strength,  and  resistance  to  corrosion;  others  are  superior  bearing 
metals.  Some  have  particular  qualifications  for  electrical  purposes ; 
others  for  high-speed  machining  for  brass-founder's  work.  One 
is  called  silver  bronze,  possessing  a  silver -white  colour. 

Metal  No.  1 :  Strongest  malleable  bronze  for  high-tensile  forgings, 
castings,  and  rods. 

Metal  No.  2 :  Silver  bronze  (improved  nickel  silver)  rods,  forgings, 
and  castings. 

Metal  No.  3 :  Specially  adapted  for  solid  drawn  tubes. 

Metal  No.  4 :  (Various  grades)  malleable  bronze,  strong  as  steel, 
tough  as  wrought  iron,  highest  resistance  to  corrosion,  for  castings, 
forgings,  stampings,  rods,  sheet,  wire,  etc. 

Metal  No.  5 :  Antifriction  bronze  for  bearing  castings. 

Metal  No.  6:  Improved  gun-metal  for  castings  of  every  descrip- 
tion. 

Metal  No.  7 :  Bronze  to  resist  high  temperature,  castings,  forg- 
ings, stampings,  rods,  etc. 

Metals  Nos.  8,  9,  9a:  Various  grades  of  white  antifriction  metals. 

Of  the  various  alloys,  the  most  used  is  No.  4.  Its  great  strength, 

164 


DELTA  METALS  165 

equalling  that  of  steel,  its  elongation,  its  toughness,  its  malleability, 
and  its  property  of  resisting  in  a  marked  degree  the  corrosive  action 
of  sea  and  mine  water,  chemicals,  gases,  etc.,  render  this  particular 
brand  the  most  useful  for  all  classes  of  work  in  which  durability, 
strength,  and  reliability  are  the  qualities  chiefly  to  be  taken  into 
consideration.  It  should  be  borne  in  mind  that  when  objects  made 
from  different  metals  or  alloys  are,  while  in  metallic  contact  with 
each  other,  immersed  in  sea  water,  brine,  or  any  other  exciting  fluid, 
galvanic  action  will  be  set  up,  which  will  bring  about  deterioration 
or  decomposition  of  the  metals.  The  rapidity  with  which  this 
deterioration  takes  place,  and  also  the  question  of  which  of  the  metals 
is  chiefly  attacked,  depends  upon  the  relative  position  of  the  different 
metals  in  the  electric  scale.  Metals  hardly  suffer  at  all  when  in  con- 
tact with  those  which  are  electro-negative  to  them ;  but  when  in 
.  contact  with  a  metal  which  is  electro-positive  towards  them  they 
are  rapidly  destroyed.  For  this  reason  delta  metal  should  never  be 
placed  in  metallic  contact  with  copper  or  gun-metal  when  immersed 
in  sea  water,  or  used  in  running  machinery  or  other  plant  which  is 
exposed  to  the  action  of  corrosive  fluids. 

From  this  it  is  clear  that  operators  should  take  care  in  the  weld- 
ing of  delta-metal  articles.     A  welding-rod  must  be  used  of  the  same 
constituents  as  the  article  being  welded,  plus  the  deoxidising  sub- 
stance.    The  results  of  tests  from  this  metal  have  shown  it  to  have 
a  tensile  strength  of  24  tons  per  square  inch,  elongation  from  30  to 
40  per  cent,  and  limit  of  elasticity  19-02  tons  per  square  inch. 
When  reheated  to  550°  C.  (a  dull  red  colour)  it  becomes  soft,  and 
is  then  one  of  the  most  malleable  copper  alloys  in  existence,  as  ] 
in  a  semiplastic  state,  in  which  it  can  be  worked  as  easily  as  wroughl 
iron,  and  can  be  stamped,  forged,  and  pressed  to  any  extent  requirec 
As  these  operations  add  50  per  cent,  strength  to  the  metal,  without 
impairing  any  of  its  other  valuable  qualities,  it  is  obvious  that,  fc 
the  majority  of  uses,  the  wrought  material  is  to  be  preferred    t 
more  so  as 'it  is  free  from  defects  which  are  sometimes 
castings,  such  as  blowholes,  etc. 

Forged  bars  of  this  alloy  show,  as  a  result  of  four  tests,  a  fc 
breaking  strain  of  344  tons  per  square  inch   with  an  elongat 
26-25  per  cent.     Its  great  strength  is  but  little  affected  by  increase 
of  temperature.     This  quality  adds  considerably  to  its  value >  i 


166  MODERN  METHODS  OF  WELDING 

metal  can  be  roughly  described  as  a  copper-zinc  alloy,  chemically 
combined  with  definite  proportions  of  iron  and  other  elements. 
The  secret  lies,  not  only  in  the  use  of  virgin  metals  in  the  exact  pro- 
portions, but  still  more  in  the  proper  methods  of  combining  these, 
and  eliminating  during  the  manufacturing  processes  certain  other 
elements  after  these  have  produced  the  desired  effect. 

The  foregoing  description  is  one  which  sets  out  the  properties 
of  a  metal  very  largely  used  in  many  workshops.  The  author 
has  not  seen  them  detailed  before;  but  he  has  had  considerable 
experience  in  the  welding  of  it,  and  articles  made  of  it  are  now 
coming  into  various  workshops  or  welding  depots  for  repairs. 

Welding-Rods. 

Welding-rods  for  use  with  delta-metal  articles  should  contain  the 
same  pure  metal,  and  also  a  trace  of  phosphorus  and  aluminium. 
These  are  added  to  the  metal  to  prevent  oxidation.  The  welding-rod 
should  be  manufactured  from  pure  metal,  and  the  constituents  or 
ingredients  uniformly  distributed  through  the  mass.  They  should 
be  made  in  sizes  from  J  to  J  inch  diameter  and  24  inches  long. 
They  are  usually  drawn  down  into  wire  of  various  thicknesses  and 
stocked  by  the  manufacturers.  They  should  also  be  made  in  various 
grades  to  .suit  the  articles  to  be  welded. 

Preparation  of  Articles. 

The  welding  of  delta  metal  is  easy  of  application,  as  the  metal 
is  very  pure.  The  area  to  be  welded  must  be  bevelled  in  the  usual 
course.  If  it  is  not  over  £  inch  thick  it  is  only  necessary  to  bevel 
one  side,  but  if  over  |  inch  thick  it  is  necessary  to  bevel  both  sides. 
Afterwards  the  weld  has  to  be  thoroughly  cleaned.  This  is  very 
important,  because  the  molten  metal  will  not  adhere  to  a  greasy 
surface. 

Preheating. — The  laws  of  expansion  and  contraction  have  neces- 
sarily to  be  considered  in  welding  this  metal.  Therefore,  it  is  desir- 
able always  to  preheat  the  articles,  and,  after  welding  sharply,  they 
should  be  returned  to  an  annealing  furnace  to  heat  up  and  allowed 
to  cool  slowly  until  quite  cold.  Apart  from  the  question  of  expan- 
sion of  the  metal,  preheating  saves  a  good  quantity  of  gases  in 
welding. 

Blowpipe  Power. — The  power  of  the  blowpipe  is,  generally  speak- 
ing, the  same  as  for  copper,  or  a  size  larger  than  that  used  for  iron 
or  steel.  The  regulation  of  the  flame  is  very  important.  This  must 


DELTA  METALS  167 

be  done  with  great  accuracy,  and  there  must  be  no  excess  of  acety- 
lene or  oxygen.  The  former  would  carbonise  the  weld,  the  latter 
would  oxidise  it.  The  oxygen  pressure  must  not  at  all  be  increased 
over  that  stated  by  the  makers.  The  flame  should  be  regulated 
till  a  clear  white  jet  or  cone  is  perceived  and  kept  at  this  until  the 
blowpipe  gets  somewhat  heated  and  the  flame  begins  to  get  less, 
when  a  little  more  acetylene  should  be  turned  on  to  make  the  even 
cone.  In  no  case  should  excess  oxygen  be  turned  on. 

Method  of  Welding. — The  preheated  and  bevelled  article  should 
be  on  the  weldjng  table,  the  blowpipe  regulated,  and  the  \\eldin  - 
rod  in  the  left  hand.  Approach  the  welding  line  at  about  J  inch 
from  the  edge,  keeping  the  white  top  of  the  flame  -?$  inch  from  the 
metal.  As  the  melting  starts,  the  blowpipe  should  be  passed  over 
to  the  edge,  and  this  melted.  At  this  period  the  welding-rod  should 
be  nearly  at  the  welding-point.  As  soon  as  the  edge  is  melted,  put 
a  little  from  the  welding-rod  into  the  molten  mass  to  fill  up  the 
bevel,  and  continue  the  movement  of  the  blowpipe  along  the  line 
of  welding  in  a  gyratory  movement,  advancing  at  the  same  time 
with  the  necessary  addition  of  the  welding-rod  to  fill  up  the  spaces 
until  there  is  enough  metal  added  to  fill  up  the  bevel.  The  welding 
must  be  continuous  when  once  started,  and  one  must  not  go  over 
the  weld  twice  without  adding  additional  welding-rod.  The  flux 
must  be  used  along  with  the  welding-rod,  and  dipped  while  hot  into 
the  flux  jar.  No  more  must  be  used  than  is  necessary— just  sufficient 
to-  clean  the  metal  and  prevent  oxidation.  When  the  weld  has  been 
completed,  the  welded  article  should  be  put  back  into  the  annealing 
furnace  and  heated  to  550°  C.,  then,  when  cold,  the  weld  may  be 
hammered. 

Failures.— These  only  occur  through  lack  of  metallurgical  know- 
ledge: adding  a  rod  of  inferior  quality;  bad  penetration;  allowing 
the  oxide  to  form  internally  in  the  metal,  forming  blowholes;  being 
too  long  on  the  weld,  and  causing  the  metal  to  become  too  liquid 
burnt,  and  oxidised;  or  melting  the  metal  to  its  boiling-point  inst 
of  its  melting-point. 

AM.  these  defects  are  easily  overcome.     They  require  a  1 
practice  and  careful  study  of  the  metallurgical  and  technical  point,. 
With  this  knowledge  failure  is  impossible. 


CHAPTER  XXVII 
ALUMINIUM 

ALUMINIUM  has  a  silvery-white  appearance,  and  is  capable  of  taking 
a  very  high  polish.  It  is  one  of  the  soft  metals,  its  hardness  being 
only  about  2-5.  Its  most  valuable  property  is  its  lightness,  the 
specific  gravity  being  2-56,  varying  slightly  with  the  impurities 
present.  Rolling,  hammering,  and  stamping  increase  its  specific 
gravity  somewhat,  that  of  worked  metal  being  as  high  as  2*7. 
The  tensile  strength  of  aluminium  castings  is  about  6  or  7  tons  per 
square  inch  in  section,  although  wire  may  reach  15  to  30  tons, 
depending  on  its  fineness. 

The  elastic  limit  is  about  3  to  4  tons  in  the  case  of  castings, 
and  may  be  as  high  as  15  tons  for  wire.  The  metal  flows  readily 
under  pressure,  and  is  therefore  both  malleable  and  ductile.  It  can  be 
rolled  into  very  thin  sheets  or  drawn  into  fine  wire.  Aluminium 
melts  readily,  its  melting-point  being  658°  C.,  and  its  boiling-point 
is  estimated  at  1,800°  C.,  being  non- volatile  in  ordinary  circum- 
stances. It  has  a  very  specific  heat,  about  0-308,  which  remains 
constant  up  to  about  800°  C.  Its  latent  heat  of  fusion  is  given  as 
100.  It  is  a  good  conductor  of  electricity,  the  conducting  power 
of  pure  aluminium  (silver  taken  as  100)  being  about  56;  but  this 
should  be  modified  by  the  presence  of  impurities,  and  by  the  condi- 
tion of  the  metal,  whether  annealed  or  not,  owing  to  its  lightness. 
For  equal  conductiveness  the  weight  of  the  aluminium  is  about 
48-5  per  cent,  that  of  copper.  It  is  used  largely  in  the  manu- 
facture of  alloys  and  for  many  purposes,  and  is  in  big  demand  for 
motor-car  castings,  whilst  its  further  use  has  been  extended  by 
the  advent  of  the  aeroplane.  Owing  to  its  low  tensile  strength,  its 
usefulness  has  been  curtailed  for  many  engineering  purposes. 
Hence  many  aluminium  alloys  have  been  brought  out  in  the  effort 
to  combine  strength  with  lightness. 

The  lightness,  low  cost,  and  ease  of  working  peculiar  to  sheet 
aluminium  have  combined  to  make  it  one  of  the  most  popular  metals 
for  the  manufacture  of  various  articles  from  the  sheet  form .  The  metal 
can  be  obtained  in  grades  from  dead  soft  to  hard  rolled.  A  square 

168 


ALUMINIUM  169 

foot  of  14  S.W.G.  sheet  aluminium  weighs  Ml  pounds,  the  same 
size  copper  weighs  3-70,  and  brass  3-56  pounds.  The  difference  in 
prices  for  the  same  sizes  is  as  follows : 

One  square  foot  of  sheet  aluminium  costs  Is.  2Jd. 

„      copper  „    3s. 

„  „  „     brass  „    2s.  6d. 

Hence  aluminium  is  much  less  than  half  the  cost  of  other  non- 
ferrous  metals ;  in  sheet  form  it  is  undoubtedly  (with  the  exception 
of  iron)  the  cheapest  material  on  the  market.  For  this  reason  sheet 
aluminium  has  come  into  extended  use  for  such  work  as  motor 
body  and  railway  coach  construction,  for  ceilings  and  panels, 
and  many  other  purposes.  The  welding  of  this  sheet  aluminium 
is  spreading  rapidly.  Operators  should  devote  much  time  to  its 
study  from  a  metallurgical  point  of  view,  so  that  when  they  come 
to  weld  it  they  may  understand  what  takes  place  when  the  heat 
of  the  flame  is  used  on  the  sheet  and  it  becomes  molten. 

Aluminium  is  without  doubt  the  most  difficult  to  weld  of  all 
metals.  This  is  largely  due  to  the  difference  in  the  fusibility  of 
the  aluminium  oxide  and  aluminium  metal.  When  two  separate 
pieces  of  aluminium  are  welded  together  at  their  edges,  by  means  of 
the  welding  flame,  the  melted  parts  do  not  flow  properly  together, 
as  is  the  case  with  iron,  where  the  melting-point  of  the  oxide  is  lower 
than  that  of  the  metal.  At  high  temperatures  aluminium  has  great 
affinity  for  oxygen.  The  molten  parts  become  covered,  under  the 
influence  of  the  welding  flame,  with  a  fine  coating  of  oxide,  which  has 
great  power  of  resistance  to  the  flame,  and,  on  cooling,  the  parts 
remain  unjoined.  Therefore,  if  aluminium  parts  are  to  be  welded 
together  properly,  this  skin  of  oxide  must  in  some  way  be  destroyed. 
This  can  be  done  to  some  extent  mechanically.  The  destruction  of 
the  covering  of  the  oxide  can  be  brought  about  by  moving  or  puddling 
the  molten  metal  of  the  weld  by  means  of  the  aluminium  wire  used 
as  a  feeding-rod  to  let  the  separate  drops,  already  formed,  flow  to  one 
another.  With  this  method,  however,  there  is  a  danger  that  the 
weld  will  be  a  failure,  not  a  homogeneous  one.  Almost  certainly  some 
part  or  other  of  the  oxide  will  remain  in  the  weld,  which  would  prob- 
ably make  it  defective.  There  are  also  many  points  to  watch  care- 
fully in  the  welding  of  aluminium.  It  is  imperative  that  it  be  sup- 
ported on  the  underside  of  the  weld.  Otherwise,  as  soon  as  the 
melting  takes  place  the  molten  metal  would  fall  through,  leaving  a 
hole  in  the  weld,  which  the  student  would  find  it  difficult  to  fill  up 
without  causing  further  holes  and  burning  the  aluminium,  rausm- 


170  MODERN  METHODS  OF  WELDING 

even  further  oxidation.  Mechanical  puddling  should  not  be  prac- 
tised, because  it  is  only  a  makeshift,  which  is  seldom  successful. 
Proper  welding — that  is,  a  homogeneous  joint — can  only  be  done 
by  very  careful  study  and  practice.  An  important  point  is  the 
use  of  a  good  flux,  which  will  cause  the  oxide  to  melt  or  break 
down  to  the  same  temperature  and  at  the  same  time  as  the  metal 
itself. 

The  difficulty  will  be  seen  when  it  is  explained  that  the  melting- 
point  of  metallic  aluminium  is  650°  C.,  whilst  the  melting-point  of 
aluminium  oxide  is  1,800°  C.  To  produce  a  flux  that  will  dissolve 
the  oxide  at  the  low  melting-point  of  the  metal,  and  at  the  same  time 
protect  the  hot  metal  from  contact  with  the  air,  is  no  easy  problem 
to  the  chemist  and  metallurgist.  It  is  only  recently  that  such  fluxes 
have  become  obtainable.  These  vary  considerably  in  their  elements 
and  compositions.  There  are  several  at  present  being  marketed. 
Each  one  pleads  it  is  the  best;  some  are  good,  but  others  are  no  use 
whatever.  If  a  good  flux  is  obtained,  there  should  be  no  reason 
(after  constant  practice)  why  operators  should  not  make  very  satis- 
factory welds  in  aluminium.  Light  hammering  of  the  weld  and 
reheating  to  a  temperature  of  about  450°  C.  are  beneficial.  Alumin- 
ium welding  is  now  quite  an  important  branch  of  the  oxy-acetylene 
welding  industry,  and  is  employed  more  particularly  in  connection 
with  brewing,  where  aluminium  is  largely  superseding  enamelled 
ware.  Fluxes  should  always  be  removed  by  washing  off  as  the 
welding  job  is  complete. 

It  is  very  important  to  choose  with  care  a  correct  blowpipe  for 
the  welding  of  aluminium  sheeting.  This  must  be  a  very  light  one, 
much  lighter  than  for  the  same  thickness  of  iron  or  steel:  just 
half  the  power  would  be  plenty.  One  must  also  be  very  careful 
to  watch  the  oxygen  pressure.  This  must  be  less  than  that  specified 
by  the  makers,  which  is  based  on  iron  and  steel.  In  all  cases  of 
welding  pure  aluminium  it  is  imperative  that  the  edges  to  be  welded 
shall  be  absolutely  clean,  and  the  welding-rod  of  the  purest  metal 
obtainable,  so  as  not  to  get  impurities  into  the  weld,  which  would 
cause  it  to  be  defective. 

Aluminium  being  of  low  melting-point,  the  operator  requires 
great  patience  and  skill  when  welding,  and  must  avoid  burning  the 
metal,  or  getting  much  above  its  melting-point,  as  the  heat  spreads 
rapidly,  especially  on  light  work. 

If  the  metal  melts  too  much  on  each  side  of  the  weld  and  makes 
too  large  a  molten  bath,  the  result  is  a  rough  and  probably  defec- 
tive weld.  Therefore,  neither  the  blowpipe  nor  the  flame  must  be 


ALUMINIUM  171 

large,  and  the  oxygen  pressure  must  be  just  sufficient  to  keep  in  the 
flame,  which  must  have  the  smallest  jet  possible. 

The  welding-rod  for  aluminium  welding  is  usually  made  from 
pure  aluminium  drawn  wire  of  diameters  for  the  various  thicknesses 
to  be  welded.  These  rods  are  usually  kept  in  stock  by  various 
factors  of  acetylene  equipment. 

It  is  imperative  that  the  rods  be  pure,  and  free  from  even  a 
trace  of  copper.  Copper  is  very  detrimental  to  welds  and  causes 
(in  moisture  or  water)  corrosion.  In  welding  pure  aluminium  parts 
it  is  not  always  necessary  to  preheat,  because  in  many  cases  the 


80.  —  FKACTURED  ALUMINIUM  GEAB  CASE. 


aluminium  article  is  able  to  stand  the  welding  without  prrheatin- 
but  hammering  and  annealing  afterwards  increase  the  strengt 
the  weld  greatly.  If  flux  has  been  used,  the  article  should  be  brushed 
in  running  water  if  possible,  because  the  flux  has  a  corroding  e 
on  the  metal. 

The  above  illustration  shows  a  motor  aluminium  crank 
which  was  welded  successfully  and  afterwards  annealed.    A  n 
job  was  made  and  in  no  way  distorted. 

In  dealing  with  alloys  the  most  important  propc-rtK-s  which  a 
desired  are  strength  and  durability  combined  with  ducti 
have  been  applied  to  commercial  specimens  of  aUoys  u  !  >o, 


172  MODERN  METHODS  OF  WELDING 

Alloys  which  are  lighter  than  aluminium  itself  generally  contain 
magnesium,  which  reduces  its  tensile  strength,  and  renders  it 
brittle  and  less  permanent  than  aluminium  itself.  An  alloy  con- 
taining approximately  76  per  cent,  of  aluminium,  21  per  cent,  of 
zinc,  3  per  cent,  of  copper,  has  an  ultimate  strength  of  12  tons  per 
square  inch.  This  is  a  mixture  from  which  motor  crank  cases  are 
frequently  made. 

Copper  alone  does  not  result  in  any  great  gain  in  beneficial  proper- 
ties, as  is  seen  by  the  fact  that  an  alloy  approximately  95  per  cent . 
aluminium  and  5  per  cent,  copper  only  reached  a  maximum  ultimate 
stress  of  8  tons  per  square  inch.  With  the  exception  of  duralumin, 
none  of  the  commercial  alloys  investigated  showed  any  remarkable 
excellence,  or,  indeed,  bore  out  the  claims  of  the  makers.  Indepen- 
dent investigation  in  the  laboratory  with  alloys  of  definite  com- 
position afforded  interesting  results  which  were  exhaustively  tabu- 
lated according  to  the  method  of  mechanical  and  heat  treatment. 
The  result  of  annealing  after  treatment  was  invariably  to  lower  the 
ultimate  strength,  while  rolling  had  the  opposite  effect. 

Sand  cast  alloy  containing  15  per  cent,  of  zinc  had  an  ultimate 
strength  of  11-19  tons  per  square  inch,  but  a  rolled  bar  reached  in 
one  case  to  17  tons,  wire  being  19  tons  per  square  inch,  even  after 
annealing  at  400°  C.  An  alloy  containing  20  per  cent,  zinc  showed 
higher  tensile  strength  all  round,  sand  cast  17  tons  per  square  inch, 
1  j  inch  diameter  rolled  bar  22 \  tons  per  square  inch.  Copper  alone 
in  small  quantities  does  not  cause  any  appreciable  improvement, 
but  it  can  be  advantageously  used  in  conjunction  with  zinc.  Experi- 
ments with  aluminium -zinc  alloys  to  which  3  per  cent,  of  copper 
was  added  showed  ultimate  strength  as  follows : 


Sand  Cast. 

Chill  Cast. 

Rolled  Bar. 

15  per  cent.  Zn 
20         „ 
26 

14-15  tons 
15-55    ,, 
18-25    „ 

14-9    tons 
14-2       „ 
22-22     „ 

23-6    tons 
23 
27-92    „ 

The  effect  of  magnesium  in  small  quantities  is,  on  the  other  hand, 
most  decided,  and  from  25  to  5  per  cent,  magnesium  has  resulted  in 
an  alloy  which,  in  rolled  condition,  possesses  an  ultimate  strength  of 
28  tons  per  square  inch.  Light  alloys  are  fairly  permanent,  if  not 
exposed  to  high  temperatures,  although  cases  of  deterioration  have 
been  known  with  alloys  of  approximately  80  per  cent,  zinc  and  20  per 
cent,  aluminium.  The  chief  trouble  is  corrosion,  which  is  marked  in 


ALUMINIUM  173 

the  case  of  alloys  containing  copper.  Indeed,  the  corrosion  of  all  light 
alloys  is  hastened  by  contact  with  copper  or  brass  when  imni' 
The  use  of  light  alloys  in  constructional  work  often  entails  welding, 
etc.,  and  great  care  should  be  exercised,  as  these  alloys  are  generally 
very  sensitive  to  all  such  treatment,  which  may  thus  lead  to  an  un- 
expected failure. 

Certain  aluminium  alloys,  generally  known  as  duralumin, 
became  materials  of  high  importance  during  the  war,  and  owe  their 
great  development  to  their  mechanical  properties.  Some  of  these 
are  singular  and  due  apparently  to  method  of  tempering.  Investi- 
gations were  made  with  a  duralumin  of  the  following  composition : 
Aluminium  93-9,  magnesium  043,  copper  3-7,  manganese  0-6, 
zinc  0-25,  silicon  0-58,  iron  O53  per  cent,  (some  of  these  minor  con- 
stituents may  probably  be  regarded  as  accidental).  Following 
the  ordinary  practice,  the  metal  was  heated  to  450°  C.,  quenched  in 
cold  water,  and  left  to  itself.  The  quenching  itself  did  not  seem 
to  change  the  properties  of  the  alloy  to  any  important  extent,  but 
the  breaking  strength,  impact  strength,  elastic  limit,  and  hardness 
increased  afterwards,  within  a  day  or  two,  while  the  elongation  and 
reduction  in  area  were  little  affected. 

Aluminium  alloy  that  is  to  be  welded  should  be  scraped  and 
cleaned,  and  if  the  stock  is  more  than  J  inch  thick  the  edges  should 
be  bevelled.  If  the  blowpipe,  when  welding,  appears  too  fierce 
a  flame,  then  this  must  be  reduced  by  (1)  reduction  of  oxygen,  and 
(2)  an  excess  of  acetylene.  This  excess  of  acetylene  does  not  injure 
aluminium  alloy,  but  lowers  the  flame  temperature,  which  is  desirable, 
owing  to  the  low  melting-point. 

Coal-gas,  instead  of  acetylene,  mixed  with  oxygen  would  do  for 
welding  aluminium,  as  it  is  a  softer  flame.  Often  good  sound  welds 
are  made  with  these  gases,  and  it  is  very  easy  to  fix  up  to  the  town 
gas;  one  precaution  must  be  taken— that  is,  the  coal-gas  must  be 
passed  through  an  hydraulic  safety  valve  the  same  as  acetylene: 
the  coal-gas  is  under  the  same  pressure  as  the  acetylene,  therefore 
it  has  to  be  used  in  the  same  way.  Also  acetylene  and  coal-gas  may 
be  used  for  the  same  service  in  welding  aluminium. 

Before  welding,  articles  of  aluminium  usually  have  to  he  heated 
up  in  the  furnace  to  about  300°  C.,  being  covered  with  asbestos  in  t he 
furnace.     As  soon  as  this  temperature  has  been  reached,  the  art  iota 
should  be  drawn  from  the  furnace,  welded  immediately,  and.  \\hni 
completed,  returned  to  the  furnace  to  be  reheated  to  300°  < 
allowed  to  cool  till  the  next  morning  in  the  furnace,  and  kept 
from  air  to  prevent  shrinkage,  cracks,  and  fractures.    Many  almmn- 


174  MODERN  METHODS  OF  WELDING 

ium -alloy  castings  may  be  welded  without  preheating,  such  as  lugs 
or  projecting  pieces  broken  off  completely.  There  is  a  great  variety 
of  alloy  mixtures,  many  of  which  are  found  in  welding  shops  in 
articles  such  as  gear  cases,  engine  cases, chain  cases  from  automobiles. 
It  is  hard  to  judge  accurately  the  composition  of  these  alloys. 

It  is  well  to  stock  welding-rods  of  three  different  compositions, 
which  should  be  as  near  as  can  be  to  the  same  analysis  as  the  articles 
to  be  welded.  From  tests  the  author  has  made,  the  three  following 
mixtures  can  be  used,  and  will  give  successful  results  if  the  articles 
are  graded  to  suit  them  : 

Aluminium         80         76         70 

Zinc         15    ,     20        26 

Copper    . .  4 

In  welding  aluminium-alloy  articles,  the  rod  must  not  be  pure 
aluminium.  It  must  be  of  the  same  materials  as  the  article  to  be 
welded.  When  welding,  a  flux  must  be  used  the  same  as  for  welding 
pure  aluminium.  Aluminium  alloy  is  not  a  ductile  metal.  Hence 
it  must  be  treated  as  one  treats  cast  iron,  and  the  phenomenon  of 
expansion  and  contraction  has  to  be  dealt  with. 

Fig.  87  is  an  alloy  gear  case,  which  plainly  tells  what  parts  are 
broken  and  have  to  be  made  good.  There  are  three  cracks  between 
the  cylinder  openings. 

The  first  procedure  on  such  a  casting  is  to  clean  it  thoroughly  and 
free  it  from  oil.  Secondly,  bevel  the  edges.  Thirdly,  prepare  a 
piece  of  sheet  iron  and  fix  inside  the  case  under  the  cracks.  This 
must  be  larger  than  the  cracks,  to  prevent  the  molten  metal  from 
falling  through.  This  will  enable  you,  too,  to  penetrate  right  through 
the  weld.  Having  got  this  all  prepared  and  placed  on  the  welding 
table  (whilst  cold),  and  put  just  in  the  position  where  welding  will 
take  place,  get  the  blowpipe,  welding-rod,  and  flux  all  ready.  Test 
the  hydraulic  safety  valve.  See  that  you  have  enough  oxygen  and 
acetylene.  All  being  ready,  and  the  tools  at  hand,  place  the  article 
to  be  welded  in  the  furnace,  and  let  it  remain  there  till  a  temperature 
of  350°  C.  is  reached.  Then  remove  from  the  furnace  and  place  in 
the  exact  position  as  when  cold,  and  immediately  commence  to 
weld.  Then  proceed  regularly  and  progressively  until  the  whole  line 
of  welding  has  been  done,  adding  at  the  same  time,  as  the  progression 
takes  place,  equal  amounts  of  the  welding-rod  to  fill  up  level  to  the 
top  of  the  edges,  dipping  the  hot  rod  in  the  flux  from  time  to  time. 
The  welding  must  be  done  quickly,  and  must  not  be  gone  over  a 
second  time.  The  tip  of  the  flame  must  not  be  allowed  to  touch  the 


ALUMINIUM  175 

metal.  Immediately  the  weld  has  been  completed,  it  should  at 
once  be  placed  in  the  furnace  again,  and  the  temperature  raised  to 
325°  C.  Afterwards  it  must  be  allowed  to  cool  slowly,  free  from 
any  draughts  or  air. 

After  cooling,  the  article  should  be  examined  to  see  if  the  weld 
has  been  homogeneous,  and  searched  for  any  further  cracks.  There 
should  not  be  any  if  the  heating  has  been  uniform.  The  weld  should 
be  cleaned  up,  or  machined  if  required,  and  tested  to  see  if  it  has 
been  distorted  in  any  way.  If  not,  the  weld  is  satisfactory. 

If  operators  will  follow  out  the  instructions  above,  they  will 


FIG.  87.—  FRACTURED  ALUMINIUM-ALLOY  GEAR  CASE. 

succeed  on  every  occasion.     Each  point  must  be  watched,  studied, 
practised,  and  practised  time  after  time. 
The  following  are  important  : 

(1)  Blowpipe  must  not  be  too  powerful;  oxygen  at  its  minimum 
pressure;  acetylene  always  slightly  in  excess. 

(2)  Articles  must  be  well  prepared,  and  placed  in  the  w<A 
position  before  placing  in  the  furnace. 

(3)  Articles  must  be  heated  to  a  temperature  of  350 

starting  welding. 

(4)  Articles  must  not  be  allowed  to  go  below  the  temperature 
of  275°  C.  while  welding.     If  they  do,  they  must  be  put  back 
the  furnace  and  reheated  to  350°  C.     The  welding  may  t 


welding,  the  article  must  be  put  into  the-  annealing 
furnace,  reheated  to  350°  C.,  and  then  allowed  to  cool  sltroly. 


176  MODERN  METHODS  OF  WELDING 

(6)  Welding-rods  must  be  approximately  of  the  analysis  of  the 
welded  article,  and  must  be  free  from  impurities. 

The  chief  uses  to  which  magnesium  is  put  are,  as  an  alloy  with 
other  metals,  and  for  intense  illuminations  of  short  duration.  When 
alloyed  with  aluminium  containing  one  or  more  other  metals,  the 
crystallisation  and  other  properties  are  modified.  As  a  scavenging 
alloy,  it  clears  up  oxide  of  other  alloys.  Because  of  its  intense  avidit}^ 
for  both  oxygen  and  nitrogen  it  is  valuable  in  aluminium,  nickel, 


FIG.  88. — ALUMINIUM-ALLOY  GEAR  CASE  REPAIRED. 

copper,  brass,  etc.,  and  in  special  steels.  In  aluminium  castings, 
for  instance,  less  than  2  per  cent,  of  magnesium  cleans  the  metal,  and 
leaves  from  J  to  If  per  cent,  in  the  casting,  about  doubling  its  tensile 
strength,  quadrupling  its  resistance  to  shock  and  jar,  and  producing 
a  much  more  easily  machined  metal. 

Fig.  88  is  an  aluminium  gear  case,  which  had  one  corner  of  the 
case  broken,  afterwards  welded  successfully. 


CHAPTER  XXVIII 
COPPER 

COPPER  stands  alone  among  the  metals  in  having  a  reddish  colour. 
It  is  capable  of  taking  a  high  polish,  but  on  exposure  to  the  air  the 
surface  darkens  considerably.  It  is  comparatively  soft  (H=3),  is 
easily  scratched  with  a  knife,  flows  readily  under  pressure,  is  both 
malleable  and  ductile,  and  can  be  rolled  into  thin  sheets  or  drawn 
into  fine  wire,  and  readily  worked  into  any  form  by  stamping  and 
spinning. 

It  is  malleable,  both  cold  and  at  a  red  heat,  .but  near  the  melt  in<_r 
point  it  becomes  brittle.  The  tensile  strength  of  cast  copper  is  about 
13  tons  per  square  inch,  but  rods  may  be  obtained  having  a  strong  h 
up  to  26  tons,  as  mechanical  working,  especially  wire  drawing,  great ly 
increases  its  strength.  When  copper  is  worked,  it  becomes  hard, 
and  loses  its  ductility  to  some  extent:  This  can,  however,  be  restored 
by  annealing.  The  specific  gravity  of  copper  is  from  8-8  to  9  (various 
figures  are  given  by  different  authorities),  depending  on  its  state. 
Castings  have  a  lower  specific  gravity  than  sheets,  and  the  specific 
gravity  of  the  latter  is  lower  than  that  of  wire. 

Copper  melts  at  1,083°  C.  and  boils  at  2,310°  C.  This  is  im- 
portant to  remember  as,  if  the  heat  in  welding  much  exceeds  the 
melting-point,  the  copper  will  be  burnt  and  full  of  blowholes. 

It  cannot  be  distilled.  Its  latent  heat  of  fusion  is  about  44 
and  its  specific  heat  roughly  0-094;  but  this  increases  as  the  tempera- 
ture rises.  The  mean  specific  heat  between  0°  and  1°  may  be  taken 
as  0-0939  to  0-00001778;  the  heat  required  to  raise  1  gramme  from 
0°  to  the  melting-point  and  melt  it  would  be  44+(-094  x  1,085)  = 
146  units.  The  coefficient  of  linear  expansion  is  0-00001596  for 
each  degree  centigrade  rise  of  temperature. 

Copper  is  an  excellent  conductor  of  both  heat  and  electricity. 
Its  heat  conductivity  is  898,  and  its  electric  conductivity  sliirh  1 1 
than  that  of  silver;  taking  the  resistance  of  the  latter  as  1.  that  of 
annealed  copper  is  about  1-003, and  thatof  hard  draxvnc..|. per  alx.iit 
1-086.     It  is  necessary  to  say  "about."  because  the  elect n 
ductivitv  is  diminished  very  considerably  by  the  slightest  traces  of 

177  1- 


178  MODERN  METHODS  OF  WELDING 

impurity.  Copper  can  now  be  obtained  so  pure  that  the  conducti- 
vity is  considerably  greater  than  that  taken  for  pure  copper  when  the 
standards  in  use  were  fixed.  The  resistance  of  a  foot  of  pure  copper 
wire,  0-001  inch  in  diameter,  is  9-612  ohms.  The  conducting  power, 
as  in  the  case  of  all  metals,  falls  as  the  temperature  rises,  the  fall  of 
conducting  power  being  29-3  per  cent,  for  a  rise  of  temperature 
from  0°  to  100°  C. 

The  principal  varieties  of  commercial  copper  are :  (1)  electrolytic ; 
(2)  best  selected  (B.S.)  tough. 

Electrolytic  copper  is  prepared  by  electro-deposition  from  solu- 
tion and  is  usually  very  pure.  It  comes  into  the  market  precipitated 
in  cakes  £  inch  thick,  deposited  on  both  sides  of  a  thin  plate  of 
copper;  or,  after  remelting,  in  ingots.  Best  selected  copper  is 
mainly  used  for  the  manufacture  of  alloys,  as  it  is  now  prepared 
from  pure  materials.  It  is  generally  specified  to  contain  not  more 
than  0-05  per  cent,  arsenic,  a  trace  of  antimony,  and  no  other  dele- 
terious material.  Tough  copper  is  the  name  given  in  this  country 
to  refined  copper  cast  into  slabs  or  billets  for  rolling  into  sheets,  rods, 
or  tubes.  It  usually  contains  from  0-25  to  0-5  per  cent,  arsenic, 
from  99-5  to  99-2  per  cent,  of  copper,  and  only  small  quantities 
of  other  impurities. 

The  British  standard  specification  for  the  testing  of  copper  is  as 
follows :  . 

Copper  Plates  for  Locomotive  Fire-Boxes. 

Tensile  Mechanical  Test. — A  standard  test-piece  having  a  gauge 
length  of  8  inches  must  show  a  tensile  breaking  strength  of  not  less 
than  14  tons  per  square  inch,  with  an  elongation  of  not  less  than 
35  per  cent. 

Bend  Test. — Pieces  of  the  plate  shall  be  tested  both  cold  and  at  a 
red  heat  by  being  doubled  over  themselves  (that  is,  bent  through 
an  angle  of  180°)  without  showing  either  crack  or  flaw  on  the 
outside  of  the  bend. 

Stay-Bolts. 

The  rods  must  be  clean,  smooth,  uniform  in  diameter,  and 
free  from  surface  defects.  The  tensile  test  must  not  be  less  than 
41  tons,  and  elongation  not  less  than  40  per  cent.  In  the  hammering 
or  crushing  down  test,  a  piece  of  rod  1  inch  long  shall  be  placed  on 
end,  and  hammered  and  crushed  down  to  a  thickness  of  |  inch 
without  showing  either  crack  or  flaw  on  the  circumference  of  the 
resulting  disc. 


COPPER  ,7!, 

Copper  Locomotive  Tubes. 

Tubes  must  contain  not  less  than  99  per  cent,  of  copper 


, 

0-35  to  0-55  per  cent,  must  consist  of  arsenic.  Tubes  must  stand 
bulging  or  drifting  without  showing  either  crack  or  flaw,  until  tin- 
diameter  of  the  bulged  end  measures  not  less  than  25  per  cent. 
greater  than  the  original  diameter  of  the  original  tube. 

Flanging  Test.—  The  tubes  must  stand  flanging  without  showier 
either  cracks  or  flaws  until  the  diameter  of  the  flange  is  not  less  than 
40  per  cent,  greater  than  the  original  diameter  of  the  tube. 

Flattening  and  Doubling-Over  Test.  —  The  tubes  must  be  capable 
of  standing  both  cold  and  a  red  heat,  without  showing  either  era*  -k 
or  flaw.  A  piece  of  tube  is  flattened  down  until  the  interior  of  tin 
two  surfaces  of  the  tube  meet.  It  is  then  bent  so  as  to  be  doubled 


FIG.  89. — PHOTOGRAPH  or  SECTION  ACROSS  A  WELD  PERFORMED  \VITIK  >n   .\ 
SPECIAL  PHOSPHOR-COPPER  WELDING-ROD. 

Notice  the  numerous  blowholes. 

over    itself,   bent   through  an  angle   of    180°,  the   bend   being  at 
right  angles  to  the  direction  of  the  length  of  the  tube. 

Hydraulic  Test. — All  boiler  tubes  shall  be  tested  by  an  internal 
hydraulic  pressure  of  at  least  750  pounds  per  square  inch. 

The  oxy-acetylene  welding  of  copper  is  not  a  stupendous  job. 
but  is  as  easy  as  with  any  ordinary  mild  steel  stocks,  provided  that 
the  necessary  instructions  are  carried  out  in  the  operation  of  welding. 
It  is  not  possible  to  weld  copper  with  an  ordinary  copper  rod.  The 
copper  when  melted  fuses,  oxidation  takes  place,  and  the  metal  is 
burnt  through  overheating,  its  temperature  reaching  boiling-point 
in  the  attempt  to  make  it  weld.  This  leaves  the  copper  weld  full  of 
blowholes  and  badly  oxidised,  as  the  above  illustration  j>n>\ 

No  matter  what  efforts  are  made  to  get  good  welds  of  eopper, 
with  only  copper  rods  they  would  not  be  a  success.     It  is neo 
to  have  some  flux  to  break  down  the  oxide.     The  best  method  is  to 


180  MODERN  METHODS  OF  WELDING 

incorporate  the  flux  in  the  welding-rod,  which  will  afterwards  be 
diffused  in  the  molten  mass  as  the  melting  takes  place.  If  the 
welding  is  done  with  a  proper  anti-oxidising  rod,  it  will  be  quite 
up  to  the  other  part  of  the  article. 

The  welding-rod  of  copper  should  contain  a  very  small  per- 
centage of  phosphorus,  with  a  trace  of  aluminium.  The  phosphorus 
is  mixed  with  the  copper  when  the  rods  are  manufactured,  in  small 
quantities,  evenly  distributed  throughout  the  rods,  thereby  securing 
equal  mixture  in  the  line  of  welding.  It  is  very  important  that  the 
proportion  of  phosphorus  shall  not  be  excessive,  as  this  causes  the 
metal  to  lack  fluidity,  and  also  leads  to  loss  of  elongation.  The 
phosphuretted  welding-rod  is  made  in  all  sizes,  from  J  to  |  inch 
diameter  (the  latter  is  used  for  welding  repairs  in  locomotive  fire- 
boxes). It  is  usually  made  in  large,  short,  round  bars,  and  drawn 
to  the  various  sizes,  which  are  then  cut  off  to  a  length  of  24  inches 
and  bundled. 

In  the  welding  of  copper  articles  it  is  usual  to  employ,  in  combina- 
tion with  the  welding,  a  flux,  or  cleaning  agent.  There  are  several 
compositions  of  these  fluxes.  One  very  good  one,  which  is  largely 
used,  consists  of  chloride  of  sodium  20  per  cent.,  boracic  acid  45  per 
cent.,  sodium  borate  35  per  cent.  Another  for  copper  alloy  is:  iron 
peroxide  35  parts,  manganese  peroxide  1  part,  magnesium  carbonate 
J  part,  alum  18  parts,  silica  3}  parts,  borax  4  parts.  Mix  and  stir 
well.  Another  consists  of  zinc  oxide  and  charcoal  in  equal  parts 
mixed  with  molasses  water  to  a  stiff  paste,  formed  into  balls  and 
then  dried. 

Copper  welds  should  be  prepared  just  in  the  same  manner  as  for 
iron  and  steel;  much  more  care  and  attention  must  be  taken  in 
cleaning  the  edges  to  be  welded.  If  they  are  not  well  cleaned,  the 
oxide  or  scale  makes  welding  more  difficult,  sometimes  causes  adhe- 
sion, or  gets  internally  into  the  weld  and  causes  blowholes. 

With  thin  copper  sheet  it  is  imperative  to  have  it  supported 
underneath.  If  this  is  not  done,  the  metal  soon  runs  through 
owing  to  its  fluidity,  and  it  is  very  difficult  to  stop  up  the  hole 
that  has  been  made.  It  is  the  custom  in  some  workshops  to  use 
a  thick  copper  plate,  which,  on  repetition  work,  assists  the  heating 
of  the  article  welded.  Sometimes  asbestos  board  is  used,  but  the 
author's  experience  is  that  asbestos  wants  renewing  too  often,  as 
the  workmen  seem  to  pull  it  to  pieces  quickly. 

Further,  there  is  a  good  smooth  joint  underneath,  and  welding 
may  go  right  through.  But  in  the  case  of  asbestos,  if  it  goes 
through,  the  blowpipe  usually  burns  or  fires  the  asbestos,  causing 


COPPER  181 

a  dazzling  light,  and  often  loaves  rough  holes  or  surface  on  the 
underside. 

The  power  of  the  blowpipe  for  copper  welding  should  he  one 
size  higher  than  that  used  for  iron  and  steel,  but  the  pressure  of 
the  oxygen  should  be  reduced  to  its  minimum.  The  larger  pip" 
is  needed  because  copper  is  a  very  high  conductor.  To  counter; t<  t . 
to  some  degree,  this  conductivity,  it  is  very  necessary,  too,  to  heat 
up  the  copper  article  before  welding. 

The  diameter  of  the  welding-rod  should  be  according  to  the  thick  - 
ness  of  the  article  to  be  welded,  but  slightly  thicker  than  the  same 
thickness  for  iron  and  steel.  The  minimum  diameter  is  16-gange, 
but  for  general  welding  a  stock  of  each  size  should  be  kept.  A  very 
good  flux  for  copper  is  2  parts  cryolite,  1  part  phosphoric  acid. 
One  has  to  be  more  careful  in  the  welding  of  copper  articles  than 
with  iron  and  steel,  although  the  same  procedure  has  to  be  followed 
out.  An  important  point  is  the  rapidity  with  which  it  must  be 
welded. 

Also  the  weld  must  not  be  gone  over  twice,  otherwise  it  will  be 
burnt,  oxidised,  and  full  of  blowholes.  Another  point,  which  must 
be  watched,  is  that  the  melting-point  of  copper  is  1,083°  C.,  and  the 
boiling-point  2,310°  C.  This  difference  in  temperature  is  vital. 
When  the  melting-point  is  reached,  welding  must  be  proceeded  with 
quickly,  and  the  blowpipe  must  be  passed  smartly  over  the  line  of 
welding,  so  as  to  just  melt  and  no  more.  The  molten  copper  will  he 
in  the  form  of  a  viscous,  thick  liquid.  The  addition  of  phosphuretted 
rod  will  make  a  good  clean  weld,  with  a  finish  as  smooth  as  the  copper 
article  itself.  There  will  be  no  oxide,  no  blowholes,  and  the  weld 
should  stand  any  ordinary  tests. 

On  the  other  hand,  if  the  welding  is  done  slowly,  and  the  blowpipe 
is  held  on  the  metal  too  long,  the  weld  becomes  too  liquid  by  tin- 
extra  heating  of  the  metal.  When  the  temperature  is  raised  to  a 
point  near  2,310°  C.,  at  which  the  copper  boils,  the  metal  is  burnt. 
Oxides  form,  which  are  absorbed  in  the  metal  as  it  cools,  and  cause 
blowholes  to  form  throughout  the  weld,  making  it  defective  and 
useless. 

Copper  is  the  greatest  conductor  of  heat  of  all  metals.     In 
welding,  preheat  it  in  a  preheating  furnace,  if   the  faeiliti. 
at  hand.     Otherwise  welding  cannot  proceed  immediate!}  ouinsr  to 
the  necessity  of  preheating  with  the  blowpipe  to  make  up  for  the 
heat  dispersing  through  the  mass. 

Procedure  in  Copper  Welding.— When  the  article  has  heen  pre- 
pared, the  blowpipe  applied,  and  the  welding-rod  held  in  the  left  hand. 


182  MODERN  METHODS  OF  WELDING 

melting  starts  at  one  end  (at  the  same  time  the  welding-rod  being 
near  the  flame) ;  the  blowpipe  is  raised  slightly  to  impinge  the  flame 
on  the  rod,  which  melts  into  the  molten  weld  and  unites  therein. 
The  blowpipe  still  continues  melting  in  a  progressive  and  continuous 
manner.  Never  let  the  white  cone  of  the  flame  touch  the  metal, 
and  take  care  to  melt,  not  burn,  the  two  edges  of  the  weld.  See 
that  the  metal  remains  a  viscous  liquid,  and  does  not  become 
"  skilly,"  or  thin  liquid.  Go  through  to  the  end  of  the  weld 
without  increasing  the  melting-point.  A  good  weld  may  be 
hammered,  bent,  and  annealed,  and  will  stand  the  tests  appearing 
in  the  first  part  of  this  chapter. 

The  tip  of  the  white  jet  of  the  flame  should  be  kept  f^-  inch 
from  the  metal.     The  treatment  after  welding  is  important,  for 


FlG.  90. — MlCROPHOTOGRAPHS  FROM  THE  REGION  OF  A  WELD  EXECUTED  WITHOUT 
SPECIAL  WELDING-ROD. 

Notice  the  separation  of  the  crystals  of  oxide  (deep  black).  The  grey  streaks  in 
the  section  on  the  right  are  the  eutectic  alloy  of  copper,  containing  4  per  cent, 
of  the  oxide. 

without  it  the  copper  is  inclined  to  be  brittle.  The  whole  article 
should  be  heated,  and  the  weld  vigorously  hammered.  After 
hammering,  heat  the  article  again  to  a  dull  red  heat  and  plunge 
suddenly  in  cold  water. 

Heated  copper  combines  with  oxygen,  forming  what  is  known 
as  cuprous  oxide.  This  oxide  is  absorbed  in  the  molten  copper, 
under  the  normal  action  of  the  blowpipe,  and  it  crystallises  on  cooling. 
When  oxidised  to  this  extent,  the  weld  is  extremely  fragile.  The 
only  means  of  overcoming  this  is,  as  before  described,  the  use  of 
a  proper,  skilfully  prepared  alloy  welding-rod  containing  a  very 
small  percentage  of  phosphorus. 

The  above  illustration  shows  the  oxide. 

The  phosphorus  welding-rod  seems  to  have  the  property  of  pre- 


COPPER  1S3 

venting  the  formation  of  blowholes,  either  by  suppressing  the  solu- 
tion of  the  gases,  or  by  aiding  their  evolution  before  the  tempera- 
ture of  solidification.  The  phosphorus  has  the  additional  advantage 
of  giving  rise  to  a  protective  varnish  on  the  surface  of  the  molten 
copper.  This  is  due  to  the  formation  of  the  oxide  of  phosphorus, 
which  combines  with  the  oxide  of  copper,  forming  a  fusible  green 
copper  phosphate.  This  substance  rises  to  the  surface  and  protects 
the  copper  from  further  action  of  the  gases  of  the  blowpipe  flame. 
Copper  welds,  when  properly  done,  should  be  hammered  whoro 
possible  at  a  red  heat,  and  then  reheated  and  plunged  in  cold  water. 
The  sizes  of  copper  phosphuretted  welding-rods  should  be  thicker 
than  for  mild  steel ;  for  instance,  J  inch  copper  should  have  a  VV  mc^ 
diameter  rod.  As  regards  expansion,  copper  must  be  treated  the 
same  as  cast  iron — that  is,  all  articles  must  be  preheated,  and 
annealed  afterwards. 

Failures  in  welding  copper  can  only  be  caused  by : 

(1)  Using  a  welding-rod  of  bad  quality. 

(2)  The  absence  of  flux  when  the  welds  are  not  absolutely  clean 

(3)  Execution  of  the  weld  before  the  copper  article  is  raised  to 
a  high  temperature. 

(4)  Bad  joining   of  the  metal  and   irregular    feeding    of    the 
welding -rod. 

(5)  The  effects  of  expansion  being  badly  opposed  both  during  and 
after  welding. 

(6)  Getting   the   copper   to   too   high    a    temperature,  greatly 
exceeding  the  melting-point. 

(7)  Going  over  the  weld  twice,  not  adding  further  welding-rod, 
thereby  causing  oxidation  and  blowholes. 

There  are  numerous  applications  in  which  the  welding  pr- 
may  be  adopted.     As  regards  loco  fire-boxes,  it  has  been  raccesafd 
in  some  cases  but  not  in  others.     For  copper  tanks,  bends,  rods  in 
electrical  work,  copper  bars  and  rings  on  armatures  it  if 
useful.     Household  copper  boilers  are  being  extensively  welda 
and  there  are  many  other  directions  in  which  welding  oouW 
take  the  place  of  brazing. 


CHAPTER  XXIX 
BRONZE 

BRONZE  may  be  considered  as  an  alloy  of  copper  and  tin,  the  former 
element  predominating.  Alloys  with  1  to  2  per  cent,  of  tin  show 
nearly  the  ductility  of  pure  copper.  They  can  be  worked  in  tho 
cold  state  under  the  hammer  more  readily  than  pure  copper.  The 
ductility  decreases  rapidly  with  an  increase  in  the  content  of  tin. 
An  alloy  containing  4  per  cent,  can  only  be  worked  with  the  hammer 
at  a  red  heat,  and  soon  cracks  when  one  attempts  to  hammer  it 
cold.  Alloys  containing  up  to  about  15  per  cent,  of  tin  can  no  longer 
be  hammered,  even  in  a  warm  state.  Alloys  with  about  9  per  cent, 
of  tin  show  the  greatest  strength  of  all  bronzes,  and  those  with 
about  15  per  cent,  possess  the  greatest  hardness  and  strength.  The 
maximum  of  hardness  and  brittleness  lies  between  28  and  35  per 
cent,  of  tin.  There  are  various  bronzes  on  the  market,  those  having 
a  percentage  of  aluminium,  manganese,  phosphor,  etc.,  being  known 
by  a  double  name — aluminium  bronze,  manganese  bronze,  etc., 
respectively.  Some  of  these  alloys  are  true  bronzes,  as  they  often 
contain  no  tin. 

Aluminium  Bronzes. 

The  proportion  of  aluminium  alloyed  with  copper  varies  from 
1  to  10  per  cent.  The  alk^s  are  as  strong  as  mild  steel,  highly 
malleable,  elastic,  and  ductile.  The  presence  of  other  metals 
impairs  the  quality.  An  alloy  containing  10  per  cent,  has  a  tensile 
strength  of  40  to  45  tons  per  square  inch. 

Manganese  Bronzes. 

These  contain  copper,  manganese,  zinc,  and  tin,  and  sometimes 
they  are  characterised  by  hardness,  elasticity,  and  strength,  com- 
bined with  toughness  and  resistance  to  corrosion.  They  can  be 
rolled  and  forged  hot.  An  important  application  is  for  the  propellers 
of  steamships.  They  are  also  used  in  general  engineering  brass- 
work.  The  manganese  is  generally  introduced  in  the  form  of  ferro- 
manganese  or  as  manganese  copper. 


BRONZE  185 

Phosphor-Bronze. 

Phosphor-bronze  contains  a  small  proportion  of  phosphorus, 
introduced  either  as  a  phosphor-tin  (obtained  by  dissolving 
phosphorus  in  molten  tin  up  to  20  per  cent,  of  phosphorus) 
or  as  phosphor-copper,  after  fusion,  or  the  ordinary  ingredient-. 
The  tin  varies  from  4  to  10  per  cent,  and  the  phosphorus  from  0-1  to  1 . 
Where  toughness  and  ductility  are  required  the  phosphorus  should 
not  exceed  0-1.  Metals  containing  more,  increase  in  hardness  and 
are -used  for  valves,  bushes,  cogwheels,  etc.  Phosphorus  should 
be  cast  at  as  low  a  temperature  as  possible. 

Silicon  Bronze. 

Silicon  bronze  contains  silicon  and  is  harder  and  stronger  than 
ordinary  bronze.  The  beneficial  effects  of  phosphorus  and  silicon 
are  generally  attributed  to  the  powerful  deoxidising  influence  they 
exert  on  account  of  their  affinity  for  oxygen.  Bronzes  do  not  absorb 
the  heat  like  copper,  although  they  absorb  it  more  than  iron  and 
steel.  There  are  several  mixtures  of  bronzes,  and  one  must  be  care- 
ful to  use  a  welding-rod  which  is  nearly  the  same  mixture  as  the 
bronze  article  being  welded.  The  table  on  p.  162  shows  several 
varieties. 

Welding- Rods. — Welding -rods  destined  for  the  efficient  welding 
of  bronzes  must  be  carefully  manufactured  from  very  pure  metal, 
and  their  constituents  must  be  the  same  as  the  article  to  be  welded, 
with  a  small  addition  of  phosphorus  and  a  trace  of  aluminium. 
These  rods  should  be  carefully  mixed  when  they  are  made,  must  not 
contain  any  impurities  whatever,  and  should  be  made  from  new 
materials.  They  are  made  in  sizes  from  £  to  |  inch  diameter  and 
24  inches  long.  They  should  be  sand-blasted  if  cast,  so  as  to  fn  ••• 
the  rods  from  the  gritty  sand. 

In  the  welding  of  bronzes  it  is  necessary  to  have  a  cleaning  flux 
to  scour  the  metal  as  it  becomes  molten.  The  flux  can  be  obtained 
from  chemists  who  are  skilled  in  the  compounding  of  these  mixtu 
A  good  flux  for  bronze  is  equal  parts  of  phosphoric  acid  and  80  per 
cent,  alcohol.  Others  are  equal  parts  of  crude  tartar  and  nitre 
burned  together ;  and  3  parts  nitre,  2  parts  argol. 

Bronze   Welding. — The  first  operation  when  one  has  a  l>nm/e 
article  is  to  see  if  it  is  bevelled.     If  not,  this  must  be  done,  and  the 
weld  properly  cleaned  and  freed  from  all  grease.     It  is  usual  to 
place  the  articles  in  the  preheating  furnace  to  get  then 
assist  welding,  and  to  prevent  fracture  from  unevin  heating.     Jt  is 


186  MODERN  METHODS  OF  WELDING 

important  if  the  article  is  unsupported  on  the  inside  to  support  it, 
as  unless  this  is  done  the  weld  cannot  be  penetrated  right  through. 
The  power  of  the  blowpipe  must  be  one  size  higher  than  that  for  iron 
and  steel  of  the  same  thickness.  The  blowpipe  must  be  properly 
regulated,  and  the  oxygen  must  not  be  in  excess,  otherwise  the  weld 
would  be  oxidised  and  burnt.  Likewise,  if  the  acetylene  is  in  excess, 
carbonisation  will  occur.  The  blowpipe  must  be  well  regulated  until 
a  clear  white  cone  is  reached,  neither  oxidising  nor  carbonising. 
Attention  must  also  be  paid  to  the  pressure  of  the  oxygen,  which 
must  not  be  more  than  that  stated  by  the  makers  of  the  blowpipe. 
This  is  very  important. 

Method  of  Welding. — The  article  should  be  fixed  up  usually  in  a 
horizontal  position.  If  broken,  the  parts  must  be  secured  to  pre- 
vent them  from  being  out  of  line  when  welded.  Proceed  with  the 
blowpipe  (already  properly  regulated)  to  heat  the  edge  of  the  line 
of  welding,  about  J  inch  from  the  actual  edge,  and  start  melting 
the  two  bevelled  edges  at  this  point.  As  soon  as  they  become 
molten,  add  a  little  welding-rod,  to  which  is  annexed  the  flux,  and 
then  bring  the  blowpipe  to  the  edge  of  the  weld.  Bring  this  to  a 
molten  state,  add  welding-rod,  fill  up  bevel,  and  proceed  forward 
with  the  welding,  at  the  same  time  giving  a  regular  gyratory  move- 
ment. Both  edges  of  the  weld  must  be  melted  together  simul- 
taneously with  the  welding-rod  with  an  occasional  dip  in  the  flux. 
See  that  the  rod  is  kept  sufficiently  in  the  molten  metal  to  fill  up 
the  bevelled  edges  to  the  same  thickness  as  the  article  being  welded. 
One  must  not  go  over  the  weld  twice  without  adding  fresh  metal. 
If  this  is  done  oxidation  takes  place  and  the  weld  is  full  of  blow- 
holes and  spoilt. 

As  soon  as  the  weld  is  done,  the  article  must  be  put  into  the 
annealing  furnace  and  heated  up  to  about  600°  C.  and  then  allowed 
to  cool  down  slowly. 

Failures  in  welding  bronzes  are  due  to : 

(1)  The  use  of  an  impure  welding-rod. 

(2)  The  overheating  of  the  metal,  making  it  too  fluid  and  caus- 
ing oxidation  and  blowholes. 

(3)  The  weld  being  gone  over  twice,  leading  to  oxidation. 

(4)  Insufficient  penetration,  causing  adhesion. 

These  failures  can  easily  be  overcome  if  operators  practise  regu- 
larly, and  test  their  pieces  until  they  find  out  that  they  have  become 
proficient. 


CHAPTER  XXX 
BRASS 

BRASS  is  an  alloy  of  copper  and  zinc,  and  is  in  most  general 
use.  It  should  only  contain  copper  and  zinc,  but  most  varieties 
contain  small  quantities  of  impurities.  Copper  and  zinc  can  be 
mixed  together  within  very  wide  limits,  the  resulting  alloys  being 
always  serviceable. 

Generally  speaking,  it  may  be  said  that  with  an  increase  in  the 
content  of  copper  the  colour  inclines  more  to  golden,  the  malle- 
ability and  softness  of  the  alloy  being  increased  at  the  same  time. 
With  an  increase  in  the  content  of  the  zinc  the  colour  becomes  lighter 
and  finally  shades  into  a  greyish-white,  while  the  alloy  becomes 
more  fusible,  more  brittle,  and  at  the  same  time  harder.  The  physi- 
cal properties  of  brass  vary  according  to  the  relative  quantities  of 
copper  and  zinc.  Alloys  containing  up  to  35  per  cent,  of  zinc  can  be 
converted  into  wire  and  sheet  in  the  cold  state  only,  those  with  from 
15  to  20  per  cent,  being  most  ductile.  Alloys  with  from  36  to  40 
per  cent,  of  zinc  can  be  worked  in  the  cold  state  as  well  as  the  hot. 
With  a  still  higher  content  the  ductility  increases  rapidly ;  and  an 
alloy,  for  instance,  from  60  to  70  per  cent,  of  zinc  is  so  brittle  that 
it  cannot  be  worked.  If,  however,  the  zinc  is  increased  up  to  a 
maximum  (70  to  90  per  cent.),  the  ductility  increases  a«r,un. 
and  the  alloy  can  be  worked  quite  well  in  the  hot  state,  hut 
not  at  red  heat.  The  strength  of  brass  is  intimately  connected 
with  its  composition,  that  containing  about  2S-f>  per  cent,  of 
zinc  showing  the  greatest  absolute  strength.  The  strength  depends 
to  a  great  extent  upon  the  mechanical  treatment  the  metal  has 
received. 

An  important  factor  in  brass  is  its  melting-point,  there  l>rin«r 
wide  deviations  in  this  respect,  which  are  readily  explained  hy  the 
great  difference  in  the  melting-points  of  the  two  constituent  metals. 
Generally  speaking,  the  fusing-point  of  brass  lies  at  about  1  v">_  1 ' 
The  mixtures  for  certain  purposes  are  legion. 

Hot-rolling  70/30  Brass.— It  is  quite  possible  to  roll  this  metal 

187 


188 


MODERN  METHODS  OF  WELDING 


hot    by   using    electrolytic   copper   and   an    electrolytic   spelter. 
The  following  is  the  mixture : 


Electrolytic  copper 
Cupro-manganese  (25  per  cent.) 
Brunner-Mond  electrolytic  spelter 


Pounds. 

68 

2 

30 


The  metal  rolls  well  at  a  bright  red  heat,  but  is  more  expensive 
than  ordinary  brass. 

Admiralty  Specification  for  Brass. 

The  composition  of  the  mixtures  used  throughout  the  whole  of 
the  work  supplied  is  to  be  as  follows.  New  metal  only  is  to  be  used 
for  castings  subject  to  steam  pressure. 


Tin.             Zinc. 

Naval  brass      

1                   37 

Brass  for  condenser  tubes      .  .          .  .             1          i         29 

Copper. 


62 

70 


All  brass  subject  to  the  action  of  sea  water  must  not  in  any  case 
contain  less  than  1  per  cent,  of  tin. 

Tensile  test-pieces  taken  from  castings  must  stand  the  following 
tests : 


Ultimate  Tensile 
Strength  Not  Less 
Than 

Elongation  in 
Length  of  2  Inches. 

Naval  brass  round  bars,  f 
Naval  brass  round  bars,  above  f 
High-tension  brass,  forged 
High-tension  brass,  cast 

14  tons 
26     „ 
22    „ 

28     „ 

7|  per  cent. 
30 
30 
25 

Naval  bars  must  be  capable  of : 

(a)  Being  hammered  hot  to  a  fine  point. 

(b)  Being  bent  cold  through  an  angle  of  75°  over  a  radius  equal 
to  the  diameter  of  the  bars.     Breaks  within  less  than  J  inch  of  the 
grip  are  not  accepted. 

General. — The  metal  castings  are  to  be  sound,  clean,  and  free 
from  blowholes,  and  no  piecing,  parching,  or  stopping  will  be  per- 
mitted. 

The  above  articles  are  often  welded,  and  one  must  study  their 
elements  in  order  to  be  able  to  execute  satisfactory  welds  on  them. 


BRASS  189 

Brasses  are  bad  conductors,  but  quite  as  fluid  as  copper.  There  are 
two  classes  of  brass — first  and  second  qualities.  The  first  mi 
930°  C.,  the  second  at  880°  C.  This  is  important,  as  if  they  are  got 
to  high  temperature  they  burn,  the  zinc  volatilises,  and  the  metal 
is  oxidised.  The  melting  of  brass  under  the  action  of  the  blo\\  pipe- 
is  accompanied  by  the  phenomena  of  the  absorption  of  gases, 
volatilisation  of  zinc,  and  oxidation. 

Operators  must  not  attempt  to  weld  brass  autogenously  with- 
out understanding  the  metallurgical  idiosyncrasy,  otherwise  success 
will  not  be  obtained.  Much  trouble  springs  from  the  volatilisation 
of  part  of  the  zinc,  which  rises  in  dense  white  fumes.  Blowholes 
then  abound,  part  of  the  zinc  is  lost,  and  the  weld  has  no  strength. 

Welding -rods  for  the  welding  of  brasses  are  manufactured  in  the 
same  way  as  copper  rods,  and  should  be  as  near  as  possible  in  com- 
position to  the  metal  being  welded,  so  as  to  keep  the  same  mixture 
of  alloy  as  in  the  article  itself.  It  is  usual  in  shops  where  a  variety 
of  brass  castings  are  welded  to  keep  sets  of  welding-rods  made  up 
to  the  different  analyses  to  suit  the  castings.  These  rods  can  be 
obtained  from  the  various  manufacturers  who  make  and  stock  them. 

Rods  for  brasses  are  made  from  the  purest  new  metal,  in  which 
a  minute  quantity  of  aluminium  should  be  evenly  incorporated 
throughout  the  length  of  the  rod.  They  are  made  in  various 
from  f\  to  J  inch  thick.  In  conjunction  with  the  rod  a  cleaning  flux 
must  be  provided,  which  dissolves  the  alumina,  prevents  the  vola- 
tilisation of  the  zinc,  and  protects  the  metal  from  oxidation.  Then 
are  many  fluxes  in  use,  but  for  general  purposes  the  following  <rive 
good  service: 

(Chloride  of  sodium       ..          ..     30  per  cent. 
(1)   j  Boric  acid  ..40 

(Borax      . .          . .          . .          . .     30       „ 

,   (Selenium  2  parts. 

(Z>  \Charcoal  1  part. 

[Sodium  carbonate  . .       5  parts. 

,Q,    I  Silica  (white  sand)        . .  •  •  15      ,, 

1  1  Coal  dust  (anthracite)  . .  . .       5      „ 

[Bone  ash  . .          •  •  . .  20     ,, 

Execution  of  Brass  Welds. 

The  edges  are  prepared  as  for  iron  and  stool,  acconlin-  to  the 
thickness,  on  one  side  or  both.     If  it  is  a  oaae  of  .  UM,M- tl: 
must  be  bevelled  wherever  the  crack  or  break  occurs,  other*  ifl 
is  sure  to  get  adhesion  or  lack  of  penetration,  excessive  ooMUmpti 


190  MODERN  METHODS  OF  WELDING 

of  gases,  burnt  metal,  and  a  defective  weld.  This  bevelling  cannot 
be  insisted  on  too  much.  The  bevel  must  be  90°  to  the  thickness 
of  the  metal — that  is,  45°  each  side.  Brass,  more  than  metal 
(aluminium  excepted),  must  be  thoroughly  cleaned,  otherwise 
adhesion  takes  place.  Brass  welds  are  easy  to  do  and  give  good 
all-round  results,  but  only  when  the  weld  line  is  properly  bevelled 
and  clean.  Also  it  is  advisable  to  preheat  the  article  to  just  under 
500°  C. 

The  blowpipe  used  is  the  same  as  in  the  case  of  copper:  one 
size  larger  than  for  iron  and  steel.  The  size  has  been  selected  to 
suit  the  thickness  of  the  articles  being  welded.  For  instance, 
J  inch  thick  requires  a  blowpipe  consuming  1-1  cubic  feet  of  acety- 
lene per  hour — that  is,  size  2  blowpipe.  The  welding-rod  for  |-inch 
thick  metal  should  be  -f^  inch  diameter. 

It  is  essential  to  have  a  rod  a  little  thicker  than  the  metal  to  be 
welded  in  the  case  of  brass.  Many  brass  articles  require  to  be 
supported  underneath  the  welding  line,  to  allow  good  penetration  of 
the  weld.  In  welding,  the  blowpipe  should  be  started  a  little  from 
the  end  (about  \  inch),  so  as  to  preheat  this  part  prior  to  doing 
the  starting  edge.  When  this  part  is  beginning  to  become  molten, 
just  put  your  blowpipe  on  to  the  edge.  At  the  same  time  add  the 
welding-rod  to  fill  and  cover  up  the  bevel,  and  then  proceed  along 
the  line  of  welding,  melting  both  edges  of  the  article  and  the  feeding- 
rod  at  the  same  time.  Continue  advancing  with  a  gyratory  move- 
ment and  adding  with  regularity  the  welding-rod,  which  must  be 
dipped  in  the  flux  from  time  to  time,  according  to  progress  made. 
Welding  must  be  continuous  until  the  whole  line  of  welding  is  com- 
plete. The  welding  must  be  rapid,  far  faster  than  with  iron  or 
steel.  Care  must  be  taken  not  to  let  the  blowpipe  stay  too  long 
on  the  weld,  or  it  will  burn,  and  will  increase  the  temperature,  and 
cause  the  metal  to  boil  and  bubble,  which  no  flux  or  rod  will  check. 
Consequently  the  weld  will  be  full  of  blowholes,  the  zinc  will  be 
reduced,  and  the  weld  will  be  oxidised,  and  therefore  useless. 

To  avoid  these  failures  one  must  not  use  a  rod  of  bad  mixture, 
nor  let  the  blowpipe  remain  too  long  on  the  weld,  otherwise  the  metal 
"  boils."  The  white  jet  must  not  touch  the  metal  within  -^r  inch. 
Brass  of  the  first  quality  can  be  hammered  and  annealed,  and  can 
stand  energetic  forging  or  stamping  without  showing  fracture. 
This  hammering  improves  considerably  its  mechanical  properties. 
Brasses  containing  55  to  65  per  cent,  of  copper  should  be  forged  hot, 
those  containing  65  to  70  per  cent,  of  copper  hammered  cold.  After 
hammering,  brass  should  be  annealed  to  just  under  500°  C. 


CHAPTER  XXXI 
AMERICAN  METHODS 

OPERATORS  will  benefit  by  an  insight  into  what  the  Americans  are 
doing  in  the  way  of  welding  processes.  Shortly  after  the  United 
States  entered  the  war,  the  Council  of  National  Defence  appointed 
an  Engineering  Committee,  which  undertook  as  one  of  its  chief 
tasks  a  study  of  the  possibilities  of  electric  welding  in  shipbuilding. 
This  Committee  was  taken  over  by  the  Emergency  Fleet  Corpora- 
tion. It  later  broadened  its  scope  so  as  to  include  gas  and  thermit 
welding.  By  its  discussions,  researches,  lectures,  and  conferem  i-s 
its  interchange  with  foreign  countries  and  its  dissemination  of  in- 
formation, the  Committee  gave  a  great  impetus  to  the  use  of  weldiiiL' 
in  America. 

Concurrently  with  this  work,  another  advance  in  welding,  with 
an  emphasis  on  gas  welding,  was  started  by  the  formation  of  the 
National  Welding  Council.  With  industry  becoming  normal,  after 
the  Armistice,  it  was  considered  desirable  to  extend  into  the  entire 
field  of  joining  metals,  and  an  effective  way  of  accomplishing  this 
was  the  foundation  of  the  American  Association  for  the  Welding 
Industry. 

The  Society  was  brought  together  in  the  manner  usual  with 
scientific  societies :  persons  from  all  branches  of  the  industry  int<  -i 
in  any  of  the  welding  processes — forge  welding,  electric  resistance 
welding,  thermit  welding,  gas  welding,  electric  spot,  butt,  scam,  and 
arc  welding.  It  will  create  and  assist  in  maintaining  the  Bureau 
of  Welding,  which  will  be  a  separate  organisation,  designed  to  take 
full  advantage  of  the  principle  of  co-operation  in  research  and 
standardisation.  Some  of  the  Society's  investigations  may  lu>  cited, 

(1)  In  arc  welding  a  determination  of  the  best  current  with 
various  sizes  of  electrodes. 

(2)  A  determination  of  proper  methods  of  procedure  in  making 
arc  and  gas  welds,  with  a  system  of  inspection  as  the  work  pro- 
gresses. 

(3)  The  acquirement  of  further  knowledge  of  the  charact* 
of  metal  as  affected  by  welding,  particularly  its  ductility  and 
action  under  repeated  tests. 


192  MODERN  METHODS  OF  WELDING 

(4)  In  gas,  spot,  or  arc  welding  methods  of  assembling  large 
structures  to  eliminate  initial  or  locked-up  stresses,  due  to  contraction 
on  cooling. 

(5)  The  ascertainment  of  a  proper  standard  for  both  producer 
and    consumer.     For  some  years  numerous  overlapping  and  con- 
flicting efforts  in  the  field  of  industrial  standardisation  have  been 
carried  out  by  more  or  less  independent  organisations,  each  according 
to  its  own  methods  of  procedure.     There  was  need,  therefore,  of 
reducing  unnecessary  effort,  and  providing  uniform  methods  that 
will  secure  in  each  case  the  co-operation  and  support  of  all  the 
organisations  whose  interests  may  be  affected. 


FIG.  91. — DUOGRAPH  WELDING  MACHINE. 

Training  of  Operators. — The  investigations  of  the  Welding  Com- 
mittee have  thus  far  shown  that  one  of  the  most  important  elements 
in  the  success  of  an  autogenous  welding  operation  is  the  skill  of  the 
operator.  To  secure  this,  uniform  methods  of  training  are  essential. 
The  Society  is  taking  an  active  part  in  planning  how  operators  should 
be  trained  and  how  their  proficiency  may  be  determined.  Some 
of  the  objects  of  the  American  Society  are  as  follows: 

(1)  To  advance  the  art  and  science  of  welding. 

(2)  To  afford  its  members  opportunities  for  the  interchange  of 
ideas  with  respect  to  the  sciences  and  art  of  welding,  and  for  the 
publication  thereof. 

(3)  To  conduct  researches  into  welding,  co-operating  with  other 


AMERICAN  METHODS 


193 


societies  and  associations,  and  with  the  Governmental  departments, 
for  the  benefit  of  the  industry  generally. 

The  illustration  on  previous  page  is  of  an  automatic  seam-weld- 
ing machine,  which  is  known  as  the  "duograph."  This  machine, 
specially  designed  for  welding  the  seams  of  drums  or  containers, 
ensuring  a  mechanical  weld  uniform  in  appearance  and  efficiency, 
comprises  a  turret-top  holding  device,  with  water-cooled  arms  and 
clamps  for  holding  the  steel  drum  in  position,  permitting  of  the 
form  being  placed  in  position  for  welding  on  the  one  set  of  arms,  while 


FIG.  92.— SHOWING  DIFFERENT  OPERATIONS  OF  THE  DUOGRAPH. 

the  form  on  the  opposite  set  is  being  welded.     The  turret  top  is 
then  swung  half-round,  the  welded  form  removed,  and  ano 
up ;  this  preparation  requires  less  time  than  the  actual  welding  of 
form  in  position.     The  blowpipe  carriage  is  moved  forward  at  a  ft 
speed  of  welding,  by  a  power-belt  motor  driven,  and  is  rover 
hand  wheel  when  the  weld  is  finished. 

Variable  speed  for  different  thicknesses  of  welding  is  obta 
by  the  use  of  cone  pulleys.     The  blowpipe  carriage  is  fitted  wit 
blowpipes,  one  above  and  the  other  below,  for  welding  bo  h 
of  the  seam  simultaneously.     For  very  light  welding,  one  btowpipe 


194  MODERN  METHODS  OF  WELDING 

only  is  required,  welding  from  one  side.  Water-cooled  blowpipes 
are  used,  connected  with  rubber  tubing  to  the  water-supply. 

This  machine  will  weld  a  seam  36  inches  long.  An  average  speed 
of  welding  is  18  inches  per  minute,  or  90  feet  per  hour  may  be  obtained 
on  16-gauge  sheets. 

The  photograph  on  p.  193  shows  different  operations  of  the  duo- 
graph. 

Fig.  93  is  of  a  medium-pressure  acetylene  generator,  15  pounds 
pressure  as  a  maximum.  This  is  designed  to  provide  acetylene 
under  suitable  conditions  and  with  proper  control,  to  meet  the 
requirements  of  the  oxy-acetylene  welding  and  cutting,  and  to 
make  possible  the  employment  of  the  positive-pressure  principle, 
utilising  acetylene  under  direct  and  appreciable  pressure,  employ- 
ing lump  carbide  for  the  generation  of  the  gas,  with  indepen- 
dent power  for  feeding  the  carbide,  the  feeding  mechanism  being 
controlled  by  the  gas  pressure  as  generated  :  the  carbide  drops  into 
large  volumes  of  water,  cools  the  gas,  and  generates  slowly. 

Safety  has  been  given  even  greater  consideration  in  the  con- 
struction of  these  plants  than  efficiency.  They  have  automatic 
feed,  carbide  to  water,  with  independent  power,  and  the  quan- 
tity of  carbide  remaining  in  the  hopper  is  constantly  indicated. 
The  acetylene  gas  is  piped  directly  from  the  generator  under 
requisite  pressure  through  a  service  pipe-line  to  the  welding 
stations,  and  regulated  by  reducing  valves,  fitted  with  pressure 
gauges  to  govern  the  proper  working  pressure. 

These  are  made  in  many  sizes  to  most  economically  meet  the 
requirements  of  the  purchaser,  and  may  be  had  with  capacity  of 
25,  50,  100,  200,  and  300  pounds  of  carbide  constituting  a  full  charge. 
These  generators  are  exceptionally  economical  compared  with  the 
low-pressure  system.  The  latter  are  used  almost  exclusively  in 
England.  The  blowpipes  used  in  low-pressure  consume  from  1-5 
to  1'3  parts  of  oxygen  to  1  part  of  acetylene.  The  medium-pressure 
generators  consume  1  part  of  oxygen  to  1  part  of  acetylene. 
Hence,  therefore,  medium -pressure  generators  save  40  to  50  per  cent, 
of  oxygen  over  the  low-pressure,  also  the  medium-pressure  gives 
40  per  cent,  more  welding.  Their  blowpipes  never  back-fire;  they 
keep  in  all  day.  Perfect  welds  are  obtained ;  no  adhesion,  no  oxida- 
tion, fully  penetrated  welds  with  98  per  cent,  tensional  stresses. 
These  advantages  are  attainable  from  the  generators  referred  to, 
which  are  known  as  the  Davis-Bournonville.  They  are  built  from 
heavy  steel  plates,  and  galvanised  after  manufacture.  They  are  used 
in  very  many  workshops  in  the  U.S.A.,  and  give  every  satisfaction. 


AMERICAN  METHODS 


This  medium -pressure  avoids  the  defects  of  the  low-pressure 
types,  which  depend  solely  on  the  injector  principle  for  the  proper 
mixture  of  the  gases  imperative  to  securing  the  best  results.  It  will 
be  readily  understood  that  in  successful  welding  a  neutral  flame 
must  be  employed,  because  if  there  is  any  excess  of  oxygen  the  metal 


FIG    93.-200  POUNDS  CARBIDE  CAPACITY,  osac  1}  POUNDS  CABBIDE. 
Height,  104  inches;  diameter,  37  inches;  weight,  850  pounds 

will  be  burnt  and  oxidised.  By  putting  the  gases  under  pn 
instead  of  depending  largely  on  the  injector  principle,  a  po. 
control  of  the  gas  is  obtained. 

Some  of  the  most  extensive  work  carried  out  ui  Amencaj »-as  a 
twelve  months'  job  for  eleven  welders,  welding  a  metal-roofed  flue, 


«JJJ«Jt/V7j          OCtViiig  U11C         V/ 

days. 

A  Corliss  compoun 
There  was  one  crack  1 
another  5  feet  long, 
would  have  been  $2,C 
reassembling;  and  th< 
less  than  six  weeks. 


AMERICAN  METHODS  197 

Others  that  would  heretofore  have  been  considered  marvellous 
operations  have  been  performed  by  the  oxy-acetylene  process, 
but  sufficient  has  been  said  to  convince  the  readers  of  its 
adaptability. 

Another  novel  but  useful  tool  is  a  blowpipe  just  brought  out  in 
America  which  is  known  and  sold  as  the  "  rego  "  blowpipe.  It  is 
claimed  that  these  torches  do  not,  and  cannot,  flash  back.  This  is 
owing  to  an  arrangement  in  the  blowpipe  which  is  designed  for 
special  supply  and  mixing  chambers.  The  acetylene  must  be  higher 


FIG.  95. — AIR-GAS  PREHEATING  TORCH  FIG.  96. — WELDING  TORCH  TIP  DIRECTLY 

FLAME  PLAYING  ON  MIXING  CHAMBER  ON   METAL   AT   WHITE  HEAT,  HELD 

OP  WELDING  TORCH  UNTIL  TIP  AND  THERE    TDLL    IT    PENETRATES.      No 

NUT  ARE  RED-HOT.     No  FLASH.  FLASH. 


pressure  than  the  oxygen,  but  not  exceeding  15  pounds.  The  claim 
is  made  that  this  invention  imparts  to  the  acetylene  a  sufficient 
speed  as  it  enters  the  mixing  chamber  and  commingles  with  the 
oxygen  to  ensure  that  at  this  point,  with  a  neutral  flame  burning  at 
the  tip,  the  speed  of  both  gases  shall  be  greater  than  that  of  the 
flame  propagation  of  the  mixtures  at  the  point  where  the  gases 
commingle. 

The  acetylene  must  be  under  greater  pressure  than  that  of  the 
oxygen  to  obtain  this  result.  The  heating  of  the  chamber  at  this 
point  to  a  sufficient  degree  to  ignite  the  mixed  gases  will  not  cause 
a  "  flash  back,"  since  the  speed  of  the  mixture  will  carry  the  flame 


198  MODERN  METHODS  OF  WELDING 

to  the  tip.  If  obstructions,  such  as  flying  particles  of  molten  metal, 
or  the  bringing  of  the  blowpipe  close,  or  up  to,  the  metal,  reduce 
the  velocity  of  the  mixtures  at  the  tip  and  tend  to  drive  the  flame 
into  the  interior  of  the  pipe,  the  acetylene,  being  under  greater  pres- 
sure, immediately  seals  the  oxygen,  causing  a  carbonising  mixture 
to  flow  from  the  mixing  chamber  to  the  tip  and  ignite.  As  the  car- 
bonising flame  cannot  flash  back,  the  acetylene  alone,  or  with  some 
quantity  of  oxygen  (depending  upon  the  size  of  the  obstruction), 
continues  to  burn  at  the  tip  until  the  obstruction  is  removed,  when 
the  oxygen  again  flows  through  in  full  volume,  producing  a  natural 
flame. 

The  American  Welding  Committee  of  the  Emergency  Fleet  Cor- 
poration, under  the  chairmanship  of  Professor  C.  A.  Adams,  has  been 


FIG.  97.— WELDING  TORCH  TIP  DIRECTLY  AGAINST  BRICK.     No  ESCAPE  FOR  HEAT 
WAVES  EXCEPT  AGAINST  TIP.    No  FLASH. 

of  great  assistance  to  the  welding  industry.  At  the  second  meeting 
held,  a  communication  was  received  from  the  U.S.A.  Shipping  Board, 
requesting  information  and  advice  on  the  most  economical  method 
of  producing  anchor  chains  in  large  quantities.  A  meeting  of  repre- 
sentatives of  chain  manufacturers  was  arranged,  and  the  work  was 
put  in  hand.  In  six  weeks  a  sample  was  submitted.  Within  six 
months  production  on  an  order  of  $1,000,000  for  chains  made  by  a 
new  process  saved  the  Government  $50,000  at  the  start.  This  new 
chain,  made  from  cast  steel,  refined  in  an  electric  furnace,  not  only 
met  the  specifications  of  the  carefully  hand-forged  chains  of  the  past; 
but  in  place  of  the  average  production  by  a  gang  of  chain-welders  of 
the  highest  skill  of  less  than  1,000  pounds  per  day,  a  foundry  unit 
with  a  10-ton  electric  furnace  produced  70  tons  of  2-inch  chain  in 
twenty-four  hours,  with  mostly  unskilled  labour. 


AMERICAN  METHODS 


199 


At  the  same  meeting  plans  for  spot  welders  of  the  portable  type, 
for  from  J  up  to  1  inch  plates,  were  discussed.  Under  the  leader 
ship  of  H.  M.  Hobart,  the  Research  Committee  investigated  the 
current  density  suitable  for  various  electrodes;  non-destructible 
methods  of  testing  welds;  the  effects  of  locked-up  stresses  in  weld- 
ing long  sections  by  rigid  or  non-rigid  methods;  the  methods  of 
holding  plates  during  welding  ;  the  effect  of  corrosion  on  welds  and 
adjacent  metal,  conducting  a  series  of  tests  on  J-inch  plates  welded 
by  employees  of  the  manufacturers 
who  supplied  the  apparatus  —  the 
choice  of  electrodes,  current  density, 
and  method  of  control  being  left  to 
the  discretion  of  the  welders.  They 
finally  submitted  standard  methods 
for  testing  electrodes  for  welds  of  all 
kinds,  and  revised  specifications  for 
electrode  wire.  These  tests  are  known 
as  the  Wirt-  Jones.  As  the  result  of 
this  instruction  propaganda,  the  Ship- 
yard Visiting  Committee  reported 
that  at  Hogg  Island  alone  hundreds 
of  thousands  of  parts  were  being 
welded  instead  of  riveted,  the  saving 
being  approximately  70  per  cent. 

Electric  welding  is  used  very  ex- 
tensively  in  America;  the  General 
Electric  Company  are  extending  the 
production  of  equipment  for  electric 
welding  for  all  classes  of  work.  I 
propose  to  show  some  of  the  equipment  in  general  use  later. 

During  the  past  few  years  the  extension  of  welding  of  all  kinds 
to  the  building  and  repair  of  ships  has  been  phenomenal,  especially 
as  regards  electric  welding.  While  electric  welding  has  been  used 
chiefly  for  iron  and  steel,  the  technique  of  the  art  for  cast  iron  and 
the  various  non-ferrous  alloys  employed  in  shipbuilding  is  being 
rapidly  developed.  The  welding  of  copper  can  be  done  with  the 
carbon  electrode.  Brass  and  bronze  castings  and  flanges  welded  to 
the  pipes  are  very  common. 


ESCAPE   FOB   SPARKS    OR  HEAT 
EXCEPT  AGAINST  TIP.     No  FLASH 


CHAPTER  XXXII 
THE  METALLURGY  OF  ARC  WELDING 

WE  have  learned  to  know,  with  a  fair  degree  of  certainty,  what  a 
steel  casting  should  be  to  be  acceptable  for  any  given  engineering 
purpose.  We, are  apt  to  be  very  particular  about  casting  when  human 
life  would  be  in  danger  by  its  failure  in  service.  This  is  true  of  all 
iron  and  steel  parts,  which  go  largely  to  the  make-up  of  our  present- 
day  necessities. 

In  building  up  and  bringing  together  many  scattered  facts  about 
the  behaviour  of  iron  and  its  alloys,  under  varying  conditions,  the 
microscope  has  played  a  very  important  role.  It  satisfies  the  natural 
curiosity  to  "  see  what's  going  on."  Merely  to  see  a  line  of  signal 
flags  on  a  destroyer,  however,  does  not  help  us  much  unless  we  know 
what  the  signals  mean.  Just  so  an  intelligent  investigation  of  a 
metallurgical  product,  like  a  weld  made  by  an  electric  arc,  involves 
considerably  more  than  a  mere  examination  of  the  metal  or  its  frac- 
ture under  the  microscope,  much  as  this  may  reveal. 

The  making  of  a  good  weld  is  essentially  a  metallurgical  problem. 
More  specifically  an  arc  weld  is  a  steel  casting  made  by  a  continuous 
process  both  as  regards  melting  and  casting.  What  we  require  is  a 
sound,  fine-grained  casting,  free  from  blowholes  and  slag  inclusions 
and  low  in  impurities.  The  casting  must  also  make  a  continuous 
and  perfect  union  with  the  plate  or  material  to  be  welded.  The 
physical  properties  of  the  weld  will  depend  upon  five  distinct  factors, 
namely:  (1)  Crystal  structure;  (2)  gas-holes;  (3)  slag  inclusion; 
(4)  impurities ;  and  (5)  composition.  These  factors  are  identical  with 
those  determining  the  properties  of  any  steel  product,  with  the  ex- 
ception that  most  of  the  latter  may  be  improved  by  heat  treatment 
or  working,  while  in  a  large  majority  of  cases  the  weld  must  be  used 
as  made.  The  order  in  which  these  factors  are  given  is  not  to  be 
taken  as  the  order  of  their  importance;  the  time  has  not  arrived 
when  such  an  order  can  be  set  down. 

Crystal  Structure. — In  studying  the  crystal  structure  of  a  large 
number  of  welds,  as  revealed  by  fracture,  it  appears  that  a  very 
fine  grain  is  produced  by  depositing  the  metal  rapidly  in  compara- 

200 


THE  METALLURGY  OF  ARC  WELDING 


201 


tively  thin  layers,  thus  preventing  the  plate  from  heating  up  suffi- 
ciently to  slow  down  the  cooling.  As  soon  as  this  occurs,  columnar 
crystals  begin  to  form,  with  a  resulting  brittleness. 


FIG.  99. — SHOWING  AREAS  AT  HIGH  MAGNIFICATION. 

It  is  often  desirable  for  other  reasons,  however,  to  maintain 
as  large  a  molten  pool  as  possible.  In  such  a  case,  the  only  way 
to  maintain  a  fine  structure  is  to  hammer  the  weld  while  hot,  to 
prevent  the  formation  of  too  coarse  a  structure.  The  cooling  effect 


FIG.  100. — NITKIDE  AREAS  IN  ELECTROLYTIC  IRON  TREATED  AS  FIG.  102. 

of  the  plate  upon  the  weld  structure  may  be  readily  observed  in 
running  a  short  length  of  weld  across  a  plate.  The  first  part  of  the 
weld  will  show  a  fine-grained  fracture,  while  a  little  farther  along 


202 


MODERN  METHODS  OF  WELDING 


a  decided  growth  begins,  gradually  changing  to  an  entirejy  coarse 
structure  as  the  plate  heats  up.  Methods  of  keeping  tL;>  plates 
cool  with  a  stream  of  water  have  been  tried  with  considerable  success 


FIG.  101. — ELECTROLYTIC  IRON,  NITROGENISED  BY  ANNEALING  IN  NH2  TWELVE 

HOURS,  750°  C. 

as  far  as  the  grain-size  is  concerned,  but  difficulties  of  manipulation 
have  prevented  its  adoption  in  practice. 

Gas-holes  are  to  be  found  in  all  electric  welds,  and  are  an  impor- 


FIG.  102. — ELECTROLYTIC  IRON,  NITROGENISED  BY  ANNEALING  IN  NH2  TWELVE 
HOURS,  750°  C.,  BUT  SUBSEQUENTLY  ANNEALED  IN  VACUUM  FOR  Two  HOURS 
AT  1,000°  C.  AREAS  SMALLER  AND  LINES  DIMINISHED  IN  NUMBER. 

tant  source  of  weakness.  Their  occurrence  is  frequently  attributed 
to  t  he  presence  of  dissolved  gases  or  gas-forming  impurities  in  the 
electrode  material.  This  is  undoubtedly  true,  but  only  to  a  limited 


THE  METALLURGY  OF  ARC  WELDING 


203 


extent.  Dissolved  or  occluded  gases  in  electrodes  are  largely  liber- 
ated as  the  metal  passes  through  the  arc  stream,  and  cannot  have 
any  considerable  effect  upon  the  deposited  metal.  They  do  affect 


FIG.  103. — EDGE  OF  WELD  MADE  WITH  COVERED  ELECTRODE,  SHOWING  COARSEN- 
ING OF  GRAIN  IN  PLATE  STOCK  BY  OVERHEATING.     (UNANNEALED.) 

the  working  of  the  electrode,  however,  as  they  cause  spluttering, 
frequently  so  bad  as  to  make  the  electrode  useless.  Experiments 
have  shown  this  to  be  particularly  true  of  highly  oxygenous 


FIG.  104. — UNANNEALED  WELD  SECTION.    WELD  MADE  WITH  STANDARD  BARE 

WIRE  ELECTRODE. 

electrode  steel.  Carbon  is  one  of  the  worst  offenders  in  producing 
gas-holes.  Always  ready  to  combine  with  oxygen,  it  finds  a  rich 
supply  in  the  metal  deposited  by  the  arc.  Carbon  momoxide  is 


204 


MODERN  METHODS  OF  WELDING 


formed  and,  owing  to  the  rapid  solidification  of  the  metal,  is  trapped. 
The  carbon  in  the  plate  also  becomes  an  important  factor  in  this 
connection.  The  carbon  in  that  portion  of  the  plate  dissolved 


FIG.  105. — LINES  IN  WELD  ANNEALED. 

into  the  welding  pool  reacts  with  the  large  percentage  of  iron  oxide 
contained  therein  and  forms  more  carbon  monoxide,  which  has  no 
opportunity  to  escape.  Welds  made  on  carbon-free  iron  do  not 


FIG.  106. — SLAG  ENCLOSED  IN  WELD. 

always  appear  in  this  particular  form,  as  may  be  seen  where  the 
most  highly  nitrogenised  sections  show  up  as  dark  patches  not  unlike 
pearlite.  These  are  shown  under  higher  magnification  in  Figs.  99 
and  100. 


THE  METALLURGY  OF  ARC  WELDING  205 

Nitrogen  is  one  of  the  most  effective  elements  for  making  steel 
brittle.  As  little  as  0-06  per  cent,  will  reduce  the  elongation  on  a 
0-2  per  cent,  carbon  steel  from  28  to  5  per  cent.  Nitrogen  is  con- 
tained in  regular  steel  only  in  very  small  amounts,  varying  from 
0-02  per  cent,  in  Bessemer  steel  to  0-005  per  cent,  in  open-hearth. 
Under  ordinary  conditions  of  fusion,  nitrogen  has  little  effect  on 
iron,  but  under  the  conditions  of  the  electric  arc  it  becomes  much 
more  active.  The  elimination  of  these  nitrides  and  oxides  must  be 
accomplished  before  the  weld  can  be  made  ductile.  Many  attempts 
have  been  made  to  do  this  by  the  alloying  of  various  scavengers  with 
the  electrode  material,  or  by  painting  them  on  or  in  .some  way 
attaching  them  to  the  electrode.  Among  other  impurities  that 
may  occur  in  a  weld,  the  sulphur  may  combine  with  the  manganese 
present. 

It  is  doubtful  if  enough  sulphur  will  remain  in  the  weld  section 
to  do  any  great  harm.  Phosphorus  forms  a  dangerous  phosphide 
eutectic  with  iron,  which  tends  to  form  a  brittle  envelope  around  the 
crystals. 

Composition. — By  composition,  given  as  the  fifth  item  influencing 
the  quality  of  the  weld,  is  meant  the  intentional  addition  of  such 
elements  as  nickel,  tungsten,  or  the  like.  These  elements  in  varying 
proportions  are  added  to  steel  to  impart  specific  properties.  One  other 
item  which  must  receive  consideration  is  the  effect  of  overheating 
the  plate  during  welding.  In  all  welds  on  fairly  heavy  sections,  this 
effect  is  always  present,  and  not  infrequently  so  weakens  the  metal 
as  to  cause  it  to  break  just  outside  the  weld,  giving  rise  to  mistaken 
ideas  that  the  weld  is  better  than  the  metal  welded.  This  overheating 
causes  a  coarsening  of  the  grain  in  the  metal  (see  Fig.  103),  and  the 
segregation  of  the  pearlite  into  large  masses  enclosed  in  ferrite  enve- 
lopes. In  general,  it  must  be  said  that  much  depends  on  the  opera- 
tor, and  much  difficulty  is  experienced  on  this  account  in  comparing 
data  from  several  sources.  Great  difference  of  opinion  still  exists 
on  many  of  these  points,  but  the  co-operation  of  the  welding  interest 
is  making  rapid  strides  towards  placing  the  whole  art  upon  a  more 
scientific  basis. 


CHAPTER  XXXIII 
BRIEF  DESCRIPTION  OF  ELECTRIC  WELDING 

ELECTRIC  butt  welding  is  a  method  of  fastening  together  suitable 
pieces  of  metal  by  the  creation  of  intense  heat  at  a  desired  place 
through  the  proper  application  of  electricity,  jointly  with  pressure 
if  butt,  seam,  or  spot  welding.  The  pressure  must  be  applied — 
if  the  work  is  to  be  efficient — in  increasing  ratio,  before  and  after 
the  application  of  the  electric  current.  The  time  taken  to  make  a 
weld  varies  from  one-fifth  of  a  second  to  four  or  five  minutes, 
according  to  the  area  welded.  The  current  required  is  of  high 
amperage  (i.e.,  volume),  but  at  low  voltage  (i.e.,  pressure). 

Volts  x  amperes  =  watts. 
1,000  watts  =  1  kilowatt. 
746  watts  =  1  horse-power. 

The  pressure  is  applied  by  hand  or  foot,  by  spring,  or  by  hydrau- 
lic means,  according  to  the  nature  and  size  of  the  work  to  be  welded. 
There  is  no  danger.  The  voltage  or  pressure  used  in  the  electrodes 
and  the  exposed  portion  of  these  machines  is  so  low — being  from 
only  2  up  to,  possibly,  5  volts  at  the  most — that  no  one  would  feel 
an  embarrassing  shock  therefrom.  It  is  about  equivalent  to  the 
voltage  or  pressure  of  an  ordinary  push-bell.  Subsequently,  heat 
has  no  effect  upon  the  weld,  unless  the  heat  is  of  such  an  intensity 
as  to  remelt  or  burn  the  metal ;  no  less  degree  of  heat  will  affect  it, 

There  are  four  main  divisions  of  electric  welding,  namely : 

/Spot  Welding. — This,  as  its  name  implies,  is  a  process  which  con- 
sists in  welding  articles  together  in  spots  instead  of  riveting  them. 
The  spots  are  usually  TV  to  J  inch  in  diameter,  seldom  larger. 

Seam  Welding. — This  is  a  process  whereby  the  overlapping  edges 
of  metal  are  joined  together  by  fusing. 

Butt  Welding.  — This  process  consists  in  bringing  together,  or 
butting,  the  two  ends  of  the  metal  rod,  bar,  etc.  (not  overlapping), 
thereby  causing  them  to  fuse  one  into  the  other. 

Arc  Welding. — This  process  is  used  for  filling  in  new  metal  along 
the  joints  to  be  welded,  the  electric  current  melting  both  faces  to 

206 


BRIEF  DESCRIPTION  OF  ELECTRIC  WELDING      207 

be  welded  at  the  same  time  as  the  electrodes,  and  filling  up  the  joint 
to  the  level  of  the  plate. 

In  spot  welding  the  electrodes  on  various  machines  may  vary 
from  f  to  |  inch  or  more  in  diameter.  They  should  be  tapered 
similarly  to  a  pencil,  at  an  angle  of  about  45°,  to  a  dull  point.  The 
point  should  be  slightly  less  than  the  diameter  of  the  weld.  This 
may  cause  a  marking  or  pitting  of  the  metal  where  the  weld  takes 
place,  which  can  be  avoided  on  the  mild  steel  about  20-  to  28-gauge 
by  using  flat  electrodes  on  one  or  both  sides.  On  thicker  materials 
one  flat  electrode  can  be  used. 

Relative  Cost  of  Riveting  and  Electric  Spot  Welding. — Riveting 
requires,  in  labour,  the  marking  off,  punching,  and  drilling  of  both 
the  plates  so  that  the  holes  match,  and  the  actual  operation  of 
riveting.  Then  there  is,  of  course,  the  purchase  cost  of  the  rivets. 
The  result  attained  is  two  pieces  of  metal  held  together  by  a  softer 
metal.  As  they  are  held  chiefly  by  the  pinch  between  the  two  rivet 
ends,  working  is  likely  to  take  place,  for  the  rivets  seldom  fit  the 
hole  tightly. 

Spot  welding  saves  the  cost  of  rivets  and  most  of  the  labour. 
There  is  no  marking  off,  no  holes  to  punch,  no  rivets  to  fit  in  the 
holes.  The  welds  can  be  applied  at  a  speed  varying,  in  continuous 
succession,  from  a  few  to  over  100  per  minute.  In  fact,  on  certain 
kinds  of  work,  200  welds  can  be  applied  per  minute.  The  welding 
machines  on  light  work  are  capable  of  making  a  weld  every  fifth 
of  a  second,  the  speed  depending  upon  the  ability  of  the  operator; 
and  in  all  repetition  work  the  spot  welding  costs  are  75  per  cent. 
less  than  riveting. 

Metals  Suitable  for  Spot  Welding. 


Platinum  to  steel  or  iron. 

Silver  to  brass,  steel  or  iron. 

Aluminium. 

Phosphor  -  bronze    to    self  and 

brass. 
Brass  to  self,  steel,  and  iron. 


Copper  to  self,  with  a  thin  brass 

insertion. 
Steel  to  self,  iron,  and  metals  as 

above. 
Iron  to  self,  steel,  and  metals  as 

above. 


Cast  iron  is  not  weldable  by  this  process. 

Butt  welding  is  principally  used  for  repetition  work,  joining 
together  bar  metal  for  crankshafts,  drop  forging,  to  stock  bars, 
tyres  for  cars  and  waggons,  bands  for  oil  drums,  rings,  chains,  mild 
steel  to  high-speed  steel,  etc.  The  scope  is  from  wire  the  thickness 
of  hair  to  15  inches  square. 

Seam  welding  is  used  for  making  watertight  joints,  where  spot 


208  MODERN  METHODS  OF  WELDING 

welding  would  not  suffice.     Seam  welding  consists  of  welding  to 
gether  the  overlapped  edges  of  two  sheets  of  metal  by  heating  under 
pressure,  with  copper  rollers  or  wheels. 

Usually  the  combined  effect  of  the  pressure  and  the  heat  causes 
the  welded  seam  to  be  nearly  the  same  thickness  as  the  original 
stock.  It  is,  however,  limited  in  its  application  to  thinner  material, 
and  aluminium  cannot  be  welded. 

Early  in  1902  there  was  a  demonstration  in  Milwaukee  of  the  use 
of  the  electric  arc  for  the  cutting  of  steel.  An  enormous  boiler  founda- 
tion had  to  be  removed  from  the  basement  of  a  building,  so  heavy  that 
local  mechanics  despaired  of  being  able  to  cut  it.  The  electric  arc 
was  requisitioned  and  soon  cut  (or,  more  correctly,  burned)  the  steel 
plate  at  the  rate  of  1  foot  in  five  minutes,  so  that  in  a  short  time  the 
whole  plate  was  divided  in  blocks  and  transported  away. 

Electric  track  welding  has  become  an  important  business. 
Rail  joints  are  welded  together  just  as  they  lie  on  the  ties.  The 
first  operation  is  sand-blasting  to  free  the  rail  ends  from  dust  and 
dirt.  An  apparatus  resembling  a  horseshoe  is  placed  over  the 
rails  where  they  join;  then,  strips  of  steel  having  been  placed  on  the 
sides  of  the  joint,  the  current  is  turned  on.  The  metal  of  the  joint 
soon  rises  to  a  welding  heat.  The  current  is  next  shut  off  and  the 
hydraulic  jaws  produce  a  great  pressure  which  completes  the  weld 
quickly.  The  current  used  is  from  25,000  to  30,000  amperes  at 
7  volts.  The  supply  at  the  welder  is  regulated  at  about  30  volts. 

Operators  often  ask,  What  is  a  volt  ?  This  is  a  term  used  to 
represent  the  pressure  of  electrical  energy.  In  steam  we  would  say 
that  a  boiler  maintains  a  pressure  of  100  pounds.  This  term  relates 
to  pressure  only,  regardless  of  quantity,  just  as  the  steam  pressure 
of  a  boiler  has  nothing  to  do  with  its  capacity. 

An  ampere  is  a  term  used  to  represent  the  current.  In  the  case 
of  steam  or  water  we  speak  of  the  carrying  capacity  of  a  pipe  in  cubic 
feet,  while  in  electricity  the  carrying  capacity  of  wires  is  given  in 
amperes. 

A  watt  is  the  electrical  unit  of  power,  and  equals  volts  x  amperes. 
One  watt  horse-power  is  equivalent  to  Ij  mechanical  horse-power 
A  kilowatt-hour,  or  k.w.h.,  is  the  electrical  equivalent  of  mechani- 
cal work,  which  would  be  stated  in  the  latter  in  the  terms  of  horse- 
power. It  means  the  consumption  of  1,000  watts  of  electrical 
energy  steadily  for  one  hour  or  any  variation  thereof  (such  as  5,000 
watts  for  twelve  minutes),  and  it  is  the  unit  employed  by  all  power 
companies  in  selling  electrical  power,  their  charges  being  based  on  a 
certain  rate  per  k.w.h.  consumed. 


BRIEF  DESCRIPTION  OF  ELECTRIC  WELDING      209 

K.v.a.  means  kilovolt  amperes,  or  volts  x  amperes -^- 1,000.  In 
any  inductive  apparatus,  such  as  a  motor  or  welding  machine,  a 
counter  current  is  set  up  within  the  apparatus  itself.  This  makes 
it  necessary  for  the  generator  to  produce  not  only  amperes  enough 
to  operate  the  motor  or  welding  machine,  but  also  enough  in  addition 
to  overcome  this  opposing  current,  although  the  actual  mechanical 
power  required  to  run  the  generator  is  only  that  sufficient  to  supply 
watts  or  electrical  energy  (volts  x  amperes)  actually  consumed  in  the 
welding  machine.  Hence  the  k.w.  demand  of  a  welding  machine 
represents  the  actual  useful  power  consumed  for  which  you  pay, 
while  the  k.v.a.  demand  represents  the  volts  x  the  total  number 
of  amperes  impressed  on  the  welding  machine-^  1,000,  to  overcome 
also  the  induced  current  set  up  within  it.  But  it  is  the  k.v.a. 
demand  that  governs  the  size  of  the  wire  to  be  used  in  the  connecting 
up  of  the  welding  machine.  K.w.  divided  by  k.v.a.  of  any  machine 
is  usually  expressed  in  percentage. 

According  to  a  report  submitted  to  the  Convention  of  the  Associa- 
tion of  Railway  Electrical  Engineers,  and  reprinted  in  the  Railway 
Review,  December  2,  1916,  ^-inch  mild  steel  electrodes  used  for 
welding  2-inch  flues  require  a  current  from  60  to  90  amperes,  with 
a  voltage  from  14  to  16;  5- inch  flues  using  a  7/W-inch  mild  steel 
electrode  require  a  current  of  from  110  to  140  amperes,  with  a 
voltage  of  16  to  20.  Mild  steel  electrodes  T\  inch  thick  require 
a  current  of  from  151  to  180  amperes,  with  voltage  from  18  to  25 
volts.  When  carbon  electrodes  |  inch  thick  are  used  for  cutting,  a 
current  is  needed  of  from  250  to  370  amperes,  with  a  voltage  of  35  to 
50  volts.  In  some  outfits,  however,  carbon  electrodes  much  smaller 
in  diameter  are  used,  one  company  employing  only  ^-inch  diameter. 

When  very  thin  sheet  is  welded  with  metallic  electrodes  with  low 
current  values.  The  following  data  for  sheet  metal  are  based  on  the 
cost  of  labour  at  Is.  6d.  per  hour,  current  at  Id.  per  kilowatt-hour. 
Metal  No.  20  gauge,  metal  electrodes  TV~inch  diameter,  current 
10  to  25  amperes,  speed  30  feet  per  hour,  average  cost  jd.  per  foot. 
Metal  18-gauge,  metal  electrodes  TV-inch  diameter,  current  35  to 
40  amperes,  speed  28  feet  per  hour,  average  cost  l]d.  per  foot. 
The  cost  of  welding  |-inch  thick  plates  by  the  arc  welding  method  is 
about  50  per  cent,  of  the  cost  of  welding  by  oxy-acetylene  on  similar 
plates.  To  weld  plates  J  inch  thick  by  arc  welding  will  cost  40  per 
cent,  less  than  oxy-acetylene.  On  1-inch  thick  plates  arc  welding 
is  15  per  cent,  cheaper  than  oxy-acetylene,  but  the  latter  is  better 
in  regards  to  expansion  owing  to  slow  heating,  which  leaves  small 

granular  section. 

14 


210  MODERN  METHODS  OF  WELDING 

The  electric  arc  claims  superiority  over  some  of  the  other 
methods.  First,  the  high  temperature  of  the  electric  ,arc  makes 
it  possible  to  reduce  rapidly  to  a  molten  state  the  metal  to 
be  welded.  The  heat  being  applied  rapidly  is  not  being  carried 
away  from  the  point  of  the  weld  by  the  heat  conductivity 
of  the  metal  fast  enough  to  lower  the  temperature  at  the  weld 
appreciably.  Secondly,  the  tools  for  performing  the  weld  are  com- 
paratively easy  to  manipulate.  The  apparatus  required  is  simpler 
than  that  used  for  gas  outfits.  Thirdly,  for  all  work,  except  very  thin 
materials,  it  is  cheapest.  Fourthly,  the  voltage  of  the  current  is  so 
low  that  the  process  is  perfectly  safe.  If  the  operator  is  provided 
with  a  proper  hood  or  shield  to  protect  him  from  the  light  and  heat 
of  the  arc,  he  is  not  exposed  to  any  danger.  The  heat  and  light  from 
the  carbon  arc  are  much  greater  than  that  from  a  metallic  arc. 

The  greatest  advantage  of  all,  probably,  is  that  the  welds  can 
be  made  overhead  and  on  vertical  seams  by  the  metallic  arc.  The 
arc  actually  carries  the  metal  particles  from  the  electrode  into  the 
weld  with  considerable  force,  so  that  even  with  an  overhead  weld 
the  metal  is  forced  clear  through  the  space  between  the  adjoining 
surfaces,  welding  them  securely.  Overhead  welding  cannot  be  done 
so  easily  by  any  other  means.  The  welds  that  are  most  commonly 
welded  by  the  electric  arc  are  mild  steel,  and  steel  castings.  For  mild 
rolled  steel  and  steel  castings,  electrodes  or  filling  rods  of  soft  iron, 
preferably  Swedish  iron,  are  used.  Tool  steel  may  also  be  welded 
with  Swedish  iron  electrodes.  Copper  has  been  welded  to  steel  by 
using  a  copper-phosphor  rod.  Brass  also  can  be  welded  with  a 
brass- aluminium  rod,  bronze  with  a  bronze-aluminium  rod. 

It  is  not  possible  to  weld  aluminium,  cast  iron,  or  copper  with 
much  success,  although  attempts  have  been  made.  These  metals 
a^e  b33t  bfb  to  the  oxy  acetylene  process,  with  which  a  good  weld 
can  always  be  made. 


CHAPTER  XXXIV 
ELECTRIC  ARC  WELDING 

r  ELECTRIC  arc  welding  is  a  fusion  process,  and  as  is  the  case  in  the 
oxy-acetylene  blowpipe  system,  the  joint  or  weld  is  obtained  by  the 
autogenous  union  of  the  metal.  The  two  pieces  are  united  by 
filling  new  material  between  them,  the  electric  current  melting  both 
faces  to  be  welded,  while  at  the  same  time  the  new  metal  of  the  elec- 
trode melts  into  the  junction  of  the  two.  The  quasi-arc  process 
is  dependent  upon  an  entirely  new  phenomenon  brought  to  light 
by  investigation,  and  is  so  different  in  method  and  result  from  the 
arc  fusion  process  that  it  merits  being  put  in  a  class  of  its  own. 
Not  only  is  this  new  process  much  more  rapid  than  any  existing 
method,  but  it  produces  a  perfect  joint,  owing  to  the  fact  that  the 
heat  introduced  into  the  weld  is  automatically  governed  by  the  nature 
of  the  special  electrodes  employed.  There  is  no  limit  to  the  size  of 
the  work  which  can  be  welded,  no  expensive  planter  machinery  is 
required,  and  the  current  consumption  is  extremely  light. 

In  this  process  the  highly  localised  heating  agency  of  the  electric 
arc  is  employed  to  bring  about  autogenous  union.  The  fusing 
starts  immediately  the  arc  is  struck,  but  under  such  conditions 
that  throughout  the  whole  operation  the  fused  adjacent  metal  is 
entirely  protected  from  all  oxidising  influences.  The  result  is 
obtained  by  the  use  of  patented  electrodes  in  conjunction  with  the 
patented  method  of  application.  The  method  of  application  is 
rendered  possible  by  the  special  character  of  the  covering  employed 
for  the  electrodes,  and  eliminates  the  necessity  for  particular  skill 
on  the  part  of  the  operator, which  is  an  essential  feature  of  other  fusion 
processes.  Uniformly  good  and  reliable  results  are  obtained,  and  no 
appreciabb  thermal  disturbance  is  caused  to  the  structures  of  the 
surrounding  metal.  It  is  necessary,  when  preparing  the  weld,  to 
have  both  edges  of  the  line  of  welding  bevelled  if  it  is  over  {\  inches 
thick. 

The  importance  of  forming  a  joint  which  shall  contain  no  trace 
of  oxide  is  so  great  as  to  deserve  particular  emphasis.  Not  only  does 
the  presence  of  oxide  greatly  reduce  the  strength  of  the  weld,  but 


212  MODERN  METHODS  OF  WELDING 

it  renders  the  joint  peculiarly  liable  to  corrosion.  But  for  the 
general  welding  in  engineering  works,  shipyards,  and  steel  foundries 
the  only  requisites,  beyond  the  electrodes,  are  a  simple  electric 
holder,  a  supply  of  current,  either  direct  or  alternating,  at  a  pressure 
of  about  105  volts,  and  a  suitable  resistance  for  regulating  the  current. 
Should,  however,  direct  current  be  available,  this  maybe  used  pro- 
vided that  a  reactance  coil  is  installed  in  each  welding  circuit. 

The  bared  end  of  the  electrode,  held  in  a  suitable  holder,  is 
connected  to  one  pole  of  the  current  supply  by  means  of  a  flexible 
cable,  the  return  wire  being  connected  to  the  work.  In  the  case  of 
small  articles  the  work  is  laid  on  an  iron  plate  or  bench,  to  which  the 
return  wire  is  connected.  Electrical  contact  is  made  by  touching 
the  work  with  the  end  of  the  electrode  held  vertically,  thus  allow- 
ing the  current  to  pass  and  an  arc  to  form.  The  electrode,  still 
kept  in  contact  with  the  work,  is  then  dropped  to  an  angle,  where 
the  arc  is  immediately  destroyed,  owing  to  the  special  covering 
passing  into  the  igneous  state,  and  as  a  secondary  conductor  main- 
taining electrical  connection  between  the  work  and  the  metallic 
core  of  the  electrode.  The  action  once  started,  the  electrode  melts 
at  a  uniform  rate,  as  long  as  it  remains  in  contact,  and  leaves  a 
seam  of  metal  perfectly  diffused  into  the  work.  The  covering 
material  of  the  electrode,  acting  as  a  slag,  floats  and  spreads  over 
the  surface  of  the  weld  as  it  is  formed.  The  fused  metal,  being 
entirely  covered  with  the  slag,  is  thereby  completely  protected  from 
all  risk  of  oxidisation.  The  slag  covering  is  readily  chipped  or 
brushed  off  when  the  weld  cools,  leaving  a  bright,  clean  metallic 
surface. 

During  the  last  two  years  much  attention  and  investigation  has 
been  carried  out  on  the  problems  involved  in  the  application  of 
the  process  to  ship  construction,  with  a  view  to  the  substitution  in 
a  large  measure  of  quasi-arc  electric  welding  for  riveting.  The 
investigation  has  been  of  a  twofold  character:  firstly,  by  a  series  of 
exhaustive  tests  to  determine  the  relative  strength  of  quasi-arc 
welding  under  all  conditions  of  stress  and  of  various  types  of  joints: 
and  secondly,  to  determine  what  modification  of  design  would  be 
necessary  or  desirable  where  welding  is  adopted.  The  results  of 
these  tests,  set  out  in  the  following  pages,  establish  the  fact  that 
a  weld  by  this  process  is  not  merely  as  strong  as,  but  is,  in 
fact,  substantially  stronger  than,  a  riveted  joint,  while  the  various 
modifications  in  design  which  have  been  evolved  and  patented 
by  the  Quasi- Arc  Company  effectually  overcome  many  difficulties 
experienced  in  present  practice  in  ship  construction;  and  this, 


ELECTRIC  ARC  WELDING  213 

coupled  with  a  notable  saving  in  weight  of  steel  used.  Inasmuch, 
also,  as  the  work  of  one  welder  is  approximately  equivalent  to  that 
of  a  squad  of  four  riveters,  there  should  be  a  substantial  increase 
in  the  rate  of  production,  accompanied  by  econom}^  in  total  cost. 

In  order  to  test  the  strength  and  suitability  of  a  welded  joint, 
it  is  not  sufficient  to  be  content  with  a  mere  tensile  or  bending  test; 
a  joint  which  could  satisfactorily  pass  such  tests  might  give  a  very 
poor  result  when  an  alternating  or  vibratory  stress  is  applied— 
indeed,  from  the  point  of  view  of  ship-designers,  the  latter  is 
probably  of  greater  importance  than  either  of  the  former,  and  for 
this  reason  special  attention  has  been  given  to  the  matter.  The 
joints  welded  by  different  processes  may  give  approximately  equal 
tensile  results,  but  show  a  marked  difference  when  subjected  to 
alternating  stresses.  Hence  the  importance  of  the  adoption  of  such 
a  process  of  electric  welding,  and  electrodes  of  such  standard 
quality,  as  will  amount  to  a  guarantee  that  a  true  crystal  union 
actually  takes  place. 

The  coatings  may  be  of  such  a  nature  as  to  supply  constituents 
that  are  burnt  out  in  the  metal  in  welding,  and  so  compensate  for 
their  loss.  In  some  electrodes  aluminium  wire  is  incorporated  under 
the  coating.  Blue  asbestos  yarn  is  specially  preferred  as  a  coating 
for  the  electrode  for  welding  mild  steel  and  iron,  as  it  is  a  reducing 
flux  and  may  be  smeared  with  a  composition  such  as  sodium  silicate 
or  aluminium  silicate,  to  the  very  fusing  temperature  of  the  yarn. 
Extreme  care  is  used  in  preparation  of  the  electrodes,  and  much 
stress  is  laid  on  the  good  and  regular  quality  of  the  metal  of  which 
they  are  composed,  and  upon  the  exactness  and  evenness  of  the 
coating.  The  metal  electrode  is  positive  to  the  work  and,  in  fusing, 
is  deposited  upon  it.  The  coating  in  melting  forms  a  vitreous  slag 
which  covers  the  weld  and  flakes  off  more  or  less  in  cooling.  The 
slag  must  be  carefully  removed  if  successive  layers  are  required. 
The  object  is  to  protect  the  weld  from  absorbing  oxygen  and  so 
avoid  deterioration  of  the  qualhVy  of  the  metal  in  the  weld.  The 
metallic  electrode  fuses  into-  the  joint  prepared  by  bevelling  the 
edges  of  the  pieces  to  be  welded,  so  that  there  is  not  properly  an  arc. 
The  electrodes  vary  from  14  to  4  s.w.g.  in  diameter  for  ordinary 
work  up  to  f-inch  thick.  The  current  is  direct,  and  the  voltage 
recommended  is  about  100,  but  much  lower  in  amperes  than 
with  Bernodos'  system,  varying  from  20  to  75  amperes  according  to 
the  thickness  operated  upon. 

Cutting  is  impossible  with  a  metallic  electrode.  The  electrode 
melts  away  in  the  operation.  If  it  touches  the  work  it  sticks  to  it. 


214  MODERN  METHODS  OF  WELDING 

Occasional  cooling  by  dipping  the  electrode  in  water  is  necessary. 
A  carbon  electrode  is  more  easily  manipulated  for  this  purpose 
With  the  metallic  electrode  positive  to  the  work,  welds  can  be  made 
upwards — that  is  to  say,  the  operator  can  work  underneath  the 
article,  and  weld  its  under  surface.  This  requires  a  particularly 
good  operator. 

Many  tests  have  been  made,  both  in  the  laboratory  and  in 
practical  service,  and  their  utility  has  been  fully  demonstrated. 
The  work,  however,  must  be  designed  to  suit  the  process,  and  the 
process  must  be  regulated  to  suit  the  work,  in  order  to  attain 
success. 

Industry  in  wartime  becomes  founded  on  an  entirely  new- 
process:  production  and  speed  of  manufacture  become  of  first 
importance;  the  cost  becomes,  to  some  extent,  secondary.  New 
methods  must  be  introduced  with  a  rapidity  unknown  in  peace- 
times, and  the  taking  of  some  chances  becomes  an  absolute  necessity. 
The  desirability  of  avoiding  machine  work  and  of  reducing  to  a 
minimum  the  labour  item,  the  necessity  of  utilising  unskilled  labour 
wherever  possible,  all  become  of  great  importance.  The  necessity 
for  long  life  is  not  always  present ;  substitutes  must  be  found  for 
many  materials  where  a  shortage  exists,  and  margins  and  factors 
of  safety  must  be  reconsidered  and,  wherever  possible,  reduced. 

The  steel  industry  with  its  allied  and  auxiliary  developments 
naturally  becomes  of  first  importance.  The  uses  of  iron  and  steel 
in  wartime  as  well  as  in  times  of  peace  are  so  manifold  as  to  pre- 
clude a  detailed  listing.  In  practically  all  the  uses  of  steel  several 
parts  must  be  joined  together  to  form  a  whole,  and  in  many  of  these 
operations  rivets  have  been  the  means  of  union  employed.  In  the 
building  of  ships,  in  the  construction  of  all  structural  material, 
wherever  steel  plate  is  used,  and  in  places  without  number,  the 
rivet  has  been  the  means  of  union  between  the  two  separate  steel 
parts.  In  accordance  with  the  law  of  economics,  wherever  a  process 
can  be  performed  in  such  a  way  as  to  show  an  advantage  in  quality, 
speed,  cost,  or  quantity,  it  must  supplant  other  methods.  Electric 
welding,  in  some  forms,  gives  every  promise  of  replacing  riveting  in 
the  enormous  field  which  the  latter  has  long  held  for  its  own.  It  is 
only  when  a  rival  appears  upon  the  field  that  the  characteristics 
and  claims  of  a  process  are  properly  investigated. 

Electric  welding  is  not  a  new  art,  but  in  its  various  forms  has 
been  used  for  many  years.  To  those  who  have  studied  the  subject, 
the  possibilities  of  arc,  spot,  butt,  and  other  forms  of  welding  are 
well  known.  The  results  that  can  be  obtained  are  matters  of  ex- 


ELECTRIC  ARC  WELDING  215 

perience,  and  years  of  actual  service  have  sufficiently  demonstrated 
the  unquestionable  reliability  of  the  process.  The  careful  and 
elaborate  scientific  investigations  now  under  way  to  determine  the 
characteristics  and  limitations  of  all  the  forms  of  electric  welding 
will  soon  place  knowledge  of  the  art  on  a  broad  basis  comparable 
to  that  of  our  best  engineering  methods.  The  repair  of  the  wilfully 
damaged  German  ships  has  been  one  of  the  most  spectacular 
demonstrations  of  the  possibility  of  the  welding  art. 

In  those  industries  in  which  iron  and  steel  parts  are  employed 
there  is  practically  no  limit  to  the  opportunities  for  employing  electric 
welding.  In  salvage  and  repair  work  it  is  being  rapidly  introduced. 
Ships,  ships,  and  more  ships  was  an  urgent  and  familiar  war  cry, 
yet  peace  does  not  release  us  from  building  ships.  In  the  course 
of  a  few  years  we  may  hope  to  see  the  electrically  welded  ship  the 
rule  instead  of  the  exception. 

Arc  welding  is  relatively  slow,  requiring  more  labour,  but  the 
apparatus  is  lighter  and  more  portable.  Electrodes  for  arc  welding 
cost  approximately  4d.  to  6d.  per  pound  bare,  and  from  lOd.  to  3s. 
per  pound  flux-covered.  There  is  a  wide  range  of  chemical  composi- 
tions, from  almost  pure  iron  and  steel  with  high  manganese,  fairly 
high  carbon.  It  is  certain  that,  where  the  strength  and  ductility 
of  a  weld  are  important,  thoroughly  skilled  operators  are  necessary, 
and  these  cannot  be  ordinarily  produced  with  less  than  six  or  eight 
weeks'  training. 

With  the  introduction  of  electric  welding  in  shipbuilding 
comes  the  necessity  of  devising  new  methods  of  assembly  and 
holding  the  plates  in  position  for  welding.  Several  methods  have 
been  proposed,  but  their  success  can  only  be  demonstrated  by  actual 
experience.  The  author  suggests  a  powerful  magnet  (such  as  one 
lifting  iron  plates  in  steel  works)  for  holding  the  plates  while  they 
are  tacked.  This  would  save  bolts  and  the  need  of  bolting.  The 
magnet  could  be  moved  from  place  to  place  by  shutting  off  the 
current.  Dependable  arc-welded  joints  can  be  made  with  an 
average  strength  of  over  90  per  cent,  of  the  plate  strength,  when 
backed  up  by  butt  straps  with  an  average  strength  of  over  100  per 
cent.  Owing  to  the  relative  brittleness  of  arc-welded-joints,  much 
fear  has  been  expressed  as  to  their  ability  to  wiffi>t^nd  long-con- 
tinued vibration  stresses  and  shocks.  Welding  affords  the  most 
simple  and  effective  means  of  making  joints  in  steel  plates  capable 
of  holding,  without  leaks,  the  warm  oil  which  the  tanks  contain 
in  service.  The  use  of  welding  has  lowered  thtf  cost  of  tank- 
making  very  materially,  and  has  reduced  the  amount  of  noise 


216  MODERN  METHODS  OF  WELDING 

in    the    tank-shops,    thus    making    the    tank-maker's   job    more 
agreeable. 

The  apparatus  required  for  electric  welding  is  comparatively 
simple  and  very  durable.  When  once  it  is  installed,  the  operator 
requires  only  his  electrodes,  and  a  source  of  electrical  energy. 
A  successful  operator  must  be  a  man  of  honest  temperament,  con- 
scientious, and  interested  to  obtain  the  best  results.  He  may  be 
taught  in  a  few  days  to  hold  the  arc  steady;  in  about  three  months 
he  may  become  an  average  operator.  It  requires  some  time  to 
acquire  the  skill  necessary  to  produce  fairly  uniform  results  in  the 
different  positions  in  which  welding  must  be  done.  The  operator 
must  acquaint  himself  with  the  flow  of  the  metal,  in  order  to  know 
definitely  whether  the  current  which  has  been  selected  for  welding 
is  too  high  or  too  low;  he  must  come  to  know  if  the  plates  being 
welded  are  penetrated  enough  with  the  arc  to  form  a  good  joint;  he 
must  observe  the  movement  and  the  condition  of  his  work,  so  that 
he  can  leave  the  least  possible  strain  in  the  completed  weld.  These 
and  many  other  points  are  to  be  learned  principally  through 
experience. 

Preparation  of  the  Work  for  Welding. 

It  is  essential  that  the  work  be  properly  prepared  before  welding 
is  begun.  .  A  thorough  study  must  be  given  to  the  job  in  hand  before 
any  attempt  is  made  to  weld.  This  study  must  be  first  applied  to 
the  effect  of  heat  on  the  parts  to  be  joined;  secondly,  to  the  accessi- 
bility of  the  parts  to  be  welded ;  thirdly,  to  the  nature  of  the  strains 
to  which  the  weld  will  be  subjected;  fourthly,  to  the  cleaning  and 
assembling  of  the  parts;  fifthly,  to  the  position  in  which  the  weld 
can  be  made;  and  sixthly,  in  what  condition  the  weld  is  to  be  left 
when  finished. 

(1)  The  effect  of  heat  is  to  produce  expansions  and  contractions 
which  must  be  provided  for  wherever  possible,  otherwise  severe 
strains  may  be  left  in  the  plates  and  welds  that  will  materially  reduce 
their  effective  strength  or  leave  the  work  in  a  warped  and  distorted 

'  condition. 

(2)  The  parts  to  be  welded  should  be  made  accessible,  so  that  the 
welding  may  be  performed  thoroughly  and  the  work  of  the  operator 
simplified. 

(3)  A  study  of  the  strains  to  which  the  work  will  be  subjected 
is  necessary  in  order  to  determine  the  kind  of  weld  that  should  be 
used.     Different  kinds  of  welds  will  be  required  according  as  the 
strain  is  a  direct  tension,  bending,  torsion,  prying,  compressive,  or 


ELECTRIC  ARC  WELDING 


21 


a  composite  one ;  and  as  the  strength  must  be  great,  as  in  a  main 
seam,  or  small,  as  in  a  caulking  weld. 

(4)  The  cleaning  and  assembly  of  parts  must  be  such  as  to  pro- 
vide clean,  proper,  and  sufficient  contact  surface  for  the  welded-in 
portion,  and  so  arranged  that  a  good  and  substantial  joint  will 
result. 

(5)  Wherever  possible,  the  joint  to  be  welded  should  be  placed  in 


FIG.  107. — USE   OF   METAL  ELECTRODE  IN  WELDING  STEEL  BANDS  TO  PRESSED 

CORRUGATIONS. 

a  position  which  will  be  the  least  arduous  for  the  welder.  Under  this 
condition  he  will  naturally  do  his  best.  Such  a  position  is  usually 
in  the  horizontal  plane.  Vertical  and  overhead  welding  may  be 
done,  and  done  well,  but  these  positions  are  more  difficult  and  tire- 
some for  the  welder. 

(6)  Usually  the  "  welt,"  or  raised  portion  of  the  weld,  is  left  on. 
But  it  is  sometimes  necessary  to  remove  this  and  have  a  plane  sur- 
face; for  example,  round  the  top  of  a  tank  which  is  to  have  a  special 


218 


MODERN  METHODS  OF  WELDING 


finish  the  entire  raised  portion  of  the  weld  may  be  removed.  Under 
these  conditions  a  light  reinforcing  weld  may  be  made  on  the  seam 
inside  the  tank  to  compensate  for  the  metal  that  has  been  removed . 
It  is  important,  if  the  weld  is  to  be  made  continuously  in  one  layer, 
to  allow  for  a  contraction  of  the  joint  as  the  weld  progresses.  Unless 
this  is  done,  undue  warping  and  excessive  internal  strains  may 
result.  The  amount  of  this  contraction  varies  slightly  with  the 


FIG.  108. — USE  OF  CARBON  ELECTRODE  WITH  METAL  FILLER  WHEN  WELDING 
THICK  STEEL  BASE  TO  THE  EDGES  OF  PRESSED  CORRUGATIONS. 


speed  at  which  the  work  is  done,  and  is  about  H  per  cent,  of  the  length 
of  the  weld.  Clamps  are  used  to  hold  the  plates  the  proper  distance 
apart,  and  these  are  gradually  released  as  the  weld  approaches 
them.  The  operator  watches  the  opening.  If  it  closes  too  quickly, 
he  hurries  his  welding.  If  it  does  not  close  quickly  enough,  he  waits 
for  it.  These  precautions  need  not  be  taken  in  very  short  butt 
welds.  Such  welds  are  too  short  to  develop  any  serious  strains. 


ELECTRIC  ARC  WELDING  219 

Welding  with  Metallic  Electrodes. 

Many  of  the  accompanying  illustrations  show  samples  of  metallic 
electrodes  welding  work  in  tank-manufacture.  These  indicate  that 
a  great  variety  of  work  can  ably  be  done  by  arc  welding  with 
metal  electrodes,  and  show  that  such  operations  are  thoroughly 
practicable,  and  the  results  neat  and  substantial. 


FIG.  109. — SEAM  PREPARED  FOR  HAND  WELDING  WITH  CARBON  ELECTRODE  AND 
OPERATOR  IN  POSITION  FOR  WELDING. 


Welding  with  Carbon  Electrode. 

The  method  applied  to  light  corrugated  tanks  differs  from  those 
used  on  boiler  plate  tanks.  The  sheet  steel  of  these  corrugated 
tanks  is  principally  of  TV  and  ^  inch  thick  and  the  carbon 
electrode  is  used  primarily  to  fuse  together  the  upturned  edges 
of  the  sheets.  The  carbon  electrode  is  also  used  in  conjunction 
with  a  metal  filler  when  placing  the  ]-inch  bottoms  in  the  corru- 
gated tanks.  The  metal  electrode,  also,  is  used  on  these  tanks 
when  welding  the  band  to  the  corrugations.  Welding,  as  applied 
to  corrugated  construction,  is  graphically  portrayed  in  the  illus- 
trations of  these  tanks. 


220 


MODERN  METHODS  OF  WELDING 


Electrodes. 

The  bare  electrodes  that  have  been  found  satisfactory  for  tank 
construction  are  as  follows : 

(1)  Norway  or  Swedish  iron. 

(2)  Toncan  iron. 

(3)  Armco  bright  hard-drawn  electric  welding  wire. 
(-4)  Roebling  bright  hard-drawn  electric  welding  wire. 

These  wires  and  the  tank  steel  have  the  following  analyses : 


Steel  Plate. 


Steel  Wire. 


1 

2 

3 

4 

Carbon          per  cent. 

0-25 

0-049 

0-10 

0-078 

0-185 

Manganese         ,, 

0-40 

0-021 

0-16 

0-041 

0-561 

Phosphorus       ,, 

0-025 

0-025 

0-025 

0-010 

0-032 

Silicon                ,, 

0-000 

0-08 

trace 

0-000 

trace 

Sulphur              „ 

0-028            0-08007 

0-046 

0-032 

0-038 

A  satisfactory  welding  wire  will  melt  and  drop  small  particles 
uniformly  into  the  weld. 

If  there  is  considerable  spluttering,  and  large  globules  drop  from 
the  welding-rod,  the  weld  will  be  very  porous,  and  the  deposited 
metal  will  be  poorly  united  to  the  plates  being  joined. 

It  is  difficult  to  give  universally  applicable  figures  covering 
amperes,  speed,  etc.,  for  electric  welding,  owing  to  the  effect  of 
conditions  under  which  the  work  is  done,  the  character  of  the  work, 
and,  to  a  very  large  extent,  the  skill  of  the  operator.  The  following 
figures  are  based  on  favourable  working  conditions  and  a  skilled 
operator.  They  are  approximations  only,  and  are  given  merely  as  a 
general  guide. 

METALLIC  ELECTRODE  WELDING. 


Electrode  Diameter  in 
Inches. 


ft 


in 

Amperes. 

Corresponding  Plate 
Thickness  in  Inches. 

25  to    50 
50  „     90 
80  ,,  150 
125  „  200 
175  „  225 

up  to  & 
s  to  |  * 
f  and  up 

The  same  size  electrode  may  be  used  with  various  thicknesses  of 
plate.     The  heavier  plates  will  require  heavier  currents.     Approxi- 


ELECTRIC  ARC  WELDING 


221 


mate  speeds  of  welding  sheet  metal  with  metallic  electrodes  and 
oxy-acetylene  welding  are  given  in  the  following  table: 


Thickness  of 
Plate. 

Speed,  Feet  per 
Hour. 

Cost  per  Foot 
of  Electric  Arc 
Welding. 

Comparative  Cost 
per  Foot  of 
Acetylene. 

iV 

20 

2-12 

1-78 

I 

16 

3-12 

4-66 

£ 

10 

7-13 

12-3 

} 

6-5                          12-3 

36-1 

I 

4-3                          19-8 

much  higher 

1 

2 

41-7 

1 

1-4                          61-3                                  „ 

Any  direct  source  can  be  used  for  welding,  but  the  voltage  of  the 
arc  must  be  reduced  to  values  of  from  50  to  20.     The  G.E.C.  have 


FIG.  110. — COMPLETE  UNIT  FOB  ELECTRIC  ABC  WELDING. 

developed  a  special  line  of  low-voltage  generators  and  controls, 
which  give  a  very  good  efficiency,  combined  with  flexibility  and 
ample  protection.  The  generator  is  wound  for  a  voltage  of  60  to 
75.  In  no  case  is  it  necessary  to  have  a  generator  of  higher  voltage 
than  this.  Lower  voltages  may  occasionally  be  used  with  low  circuit 
values.  The  generators  are  usually  furnished  as  a  part  of  a  motor- 
generator  set,  although  they  can  be  supplied  for  a  belt  drive  if 
desired.  The  motor-generator  set  is  the  most  desirable  equipment 
for  several  reasons :  it  is  a  self-contained  unit  and  does  not  demand 
any  attention  when  running;  the  maintenance  is  low;  the  weld- 


222 


MODERN  METHODS  OF  WELDING 


ing  circuits  and  the  shop  circuits  are  electrically  independent,  so 
that  short  circuits  in  the  welding  circuit  will" not  seriously  interfere 
with  the  shop  circuit;  the  voltage  on  the  welding  circuit  can  be 
regulated,  if  desired,  by  adjustment  of  the  generator  field  rheostat. 
The  control  equipment  consists  of  a  main  generator  panel,  with  or 
without  a  welding  control  circuit,  with  a  separate  auxiliary  panel 
for  each  operator.  The  equipment  mounted  on  these  panels  is 
shown  herewith.  In  addition,  there  is,  in  series  with  the  arc,  a  grid 
rheostat  for  varying  the  current  by  means  of 
a  dial-switch  shown  on  the  panel. 

The  automatic  control  equipment  gives 
thorough  protection  to  the  generator  without 
afFocting  other  operators  whose  welding  cir- 
cuits may  be  connected  to  the  same  generator ; 
this  equipment  consists  of  a  protective  relay 
controlling  a  shunt  contactor  in  the  welding 
circuit.  The  setting  of  the  dial- switch  on  the 
welding  panel  determines  the  amount  of  re- 
sistance in  series  with  the  arc,  and  therefore 
controls  the  current  used.  This  is  regulated 
by  the  current  required  by  work  done.  Before 
starting  the  arc  the  operator  must  set  the 
dial-switch  for  the  amount  of  current  required, 
so  that  on  starting  the  circuits  are  in  noimal 
running  position.  There  is  no  necessity  for 
having  any  relays  or  switches  open  or  closed, 
or  in  any  way  changing  or  disturbing  the 
electrical  circuit  in  order  to  weld. 

Where  welding  by  the  carbon  electrode  is 
to  be  done,  thin  metal  can  be  welded  using 
150  to  250  amperes.  Medium  welding  by  this 
process  requires  from  250  to  350  amperes. 
Heavy  welding  will  require  400  to  600  amperes. 
Where  cutting  is  to  be  done  by  the  carbon 
arc,  the  capacity  of  the  set  depends  on  the 
cutting  speed  required.  For  light  metal  where 

speed  is  not  important,  300  amperes  are  sufficient,  but  where  the 
metal  is  2  inches  thick  or  more  it  is  desirable  to  use  heavier 
currents.  For  this  purpose  up  to  1,000  amperes  can  be  used. 

In  addition  to  the  equipment  and  accessories  previously  described, 
special  jobs  render  it  desirable  to  have  on  hand  other  miscellaneous 
pieces  of  equipment.  Odd  pieces  of  copper  and  carbon  blocks  are 


FIG.  111.— WELDING 
PANEL. 

Setting  of  the  dial-switch 
determines  the  amount 
of  resistance  in  series 
with  the  arc. 


ELECTRIC  ARC  WELDING  223 

of  much  assistance  as  "  dams"  in  holding  the  metal  in  place.  In 
cases  where  the  weld  must  be  smooth  on  one  side,  a  piece  of  copper 
or  carbon  is  held  against  the  weld,  and  the  metal  filled  against  it. 
Iron  and  steel  can  be  used  if  care  is  taken  not  to  weld  it.  In  filling 
a  hole,  the  bottom  is  often  closed  by  holding  a  plate  of  copper  or 
carbon  against  it  until  sufficient  is  filled  in.  Care  should  be  taken 
to  flow  the  molten  metal  against  the  guide-pieces,  not  to  allow  the 
arc  to  play  directly  on  them.  Otherwise  the  weld  will  probably  be- 
come contaminated  by  this  material,  or  else  the  guide-pieces  may 
be  welded  solid  and  not  easily  removed.  A  steel  wire  scratch-brush 
is  used  to  remove  slight  scale  and  rust  before  commencing  the  weld, 
also  at  intervals  during  welding  —  as  when  changing  electrodes. 
For  small  work  the  positive  lead  may  be  bolted  to  an  iron  plate, 
forming  the  top  of  a  work-bench.  The  work  may  be  set  on  this 
bench,  the  contact  being  sufficient  to  carry  the  current.  In  many 
cases  a  vice  mounted  on  the  table  will  be  found  useful. 

If  the  work  is  too  large  for  the  table  it  may  be  set  beside  the 
table  and  a  bar  laid  across  it.  This  will  provide  sufficient  current 
carrying  capacity,  providing  that  scale  and  rust  do  not  prevent 
contact.  A  convenient  terminal  for  the  positive  cable  consists  of 
a  copper  hook  of  proper  size,  to  which  the  cable  is  bolted.  If  weld- 
ing is  to  be  done  in  a  room  where  other  employees  are  doing  different 
work,  screens  should  be  provided  around  the  welding  operator. 
They  should  be  high  enough  to  prevent  the  light  striking  a  large 
part  of  the  ceiling,  since  the  flicker  of  this  light  would  probably 
affect  other  workmen.  The  effect,  while  probably  not  injurious, 
would  be  irritating.  White  walls  and  ceilings  should  be  avoided 
in  a  welding  room.  Gas-burners  or  annealing  furnaces  for  pre- 
heating fire-bricks,  sand,  or  asbestos  sheeting  for  covering  are  useful, 
especially  in  cast-ironwork,  which  in  many  cases  should  be  preheated 
uniformly  to  a  red  heat  and  welded  at  that  temperature.  A  recep- 
tacle of  water  is  desirable  in  which  the  electrode  holder  can  be  cooled 
when  it  becomes  too  hot  after  continual  use. 

Some  operators  feel  that  gloves  are  necessary  to  protect  the  hands 
from  the  arc.  In  many  cases,  however,  the  operator  finds  gloves 
to  be  in  the  way,  especially  when  working  writh  a  metallic  electrode. 
If  desired,  however,  any  leather  glove  will  give  sufficient  protection 
to  the  skin  of  the  hands,  which  is  much  less  sensitive  than  the  skin  on 
the  other  parts  of  the  body.  The  arms,  face,  and  neck  should,  how- 
ever, be  covered,  since  exposure  of  these  parts  will  probably  result 
in  burns  similar  to  sunburn,  which,  while  not  serious,  are  painful. 

Flux. — It  is  the  experience  of  a  great  majorit}'  of  operators  that 


224  MODERN  METHODS  OP  WELDING 

flux  of  any  kind  is  unnecessary  in  welding.  Further,  that  it  is  a 
source  of  danger,  in  that  there  is  liability  of  contaminating  the 
weld.  If  the  work  is  kept  clean  by  brushing  at  equal  intervals, 
and  ordinary  care  taken  in  the  operation  of  the  arc,  a  good  weld 
can  be  made  without  flux.  If  these  precautions  are  lacking,  flux 
will  not  make  a  good  weld. 

Preparation  of  Welds. — Metal  that  is  clean  is  much  more  likely 
to  make  a  good  strong  weld.  Scale,  rust,  grease,  soot,  and  any  foreign 
matter  will  contaminate  the  weld.  Such  inclusions  necessarily 
weaken  it,  or  else  make  it  hard.  Impurities  may  also  make  the 
metal  porous  and  spongy,  owing  to  the  liberation  of  the  gases. 
^Pieces  of  foreign  matter  may  prevent  the  molten  metal  from  filling 
all  the  parts  of  the  weld  and  cause  cavities.  Various  methods  of 
cleaning  are  in  use:  pickling  for  small  parts,  washing  with  petrol 
or  lye,  boiling  with  lye  and  sand,  sand-blasting,  chiselling,  scratch - 
brushing,  etc. — the  method  depending  on  the  local  conditions. 
Preparatory  to  welding  locomotive  tubes  to  the  sheets,  it  is  sometimes 
advantageous  to  send  the  locomotive  out  for  a  run  to  burn  off  the 
grease,  and  then  clean  off  the  oxide  and  soot  by  sand-blasting.  Another 
method  is  to  heat  the  boiler  to  normal  by  steam  pressure,  and  then 
to  clean  by  sand-blasting  or  scratch-brushing.  Washing  with  lye 
will  also  remove  the  grease.  In  welding  heavy  sections,  where  it  is 
necessary  to  deposit  several  layers  of  metal  on  the  surface,  the 
preceding  layer  should  always  be  cleaned  before  starting  the  next. 

Sections  of  ^  inch  or  less  in  thickness  need  not  be  bevelled,  but 
they  should  be  separated  about  -J  inch.  Thicker  sections  should 
be  bevelled  to  give  a  total  angle  of  60°  as  well  as  separated  £  inch. 
In  some  special  cases  angles  as  low  as  40°  may  be  necessary,  while 
as  high  as  90°  may  be  used;  but  an  average  and  safe  value  is 
60°.  Still  heavier  sections  may  be  bevelled  both  sides  and  the  weld 
made  from  both  sides. 

In  the  latter  case  a  layer  should  be  put  on  one  side,  then  a  layer 
on  the  other,  to  prevent  warping ;  for  long  seams  the  edges  should  be 
kept  about  J  per  cent,  apart,  at  the  opposite  end  to  which  the 
welding  is  started;  at  the  end  where  the  weld  starts  this  is  to  be 
kept  open  |  inch.  This  takes  some  of  the  expansion  and  contrac- 
tion of  the  metal  in  the  sheet.  Another  method  of  reducing 
contraction  is  to  put  in  short  sections  at  intervals,  welding  in 
one  layer  at  a  time,  starting  at  the  centre  and  working  altern- 
ately to  each  end.  Then  put  a  layer  on  the  open  sections,  and 
continue  in  the  same  way  until  the  weld  is  complete,  the  welded 
section  of  any  layer  below  or  above  the  joints  being  broken 


ELECTRIC  ARC  WELDING  225 

as  in  laying  brickwork.  Still  another  method :  ~  instead  of  be- 
ginning the  weld  at  the  edge  of  the  plate,  start  it  some  distance  in 
and  weld  towards  the  edge  of  the  plate.  Then  a  second  weld  is 
started  the  same  distance  ahead  of  the  first  section.  This  method 
is  called  back- welding.  The  length  of  each  section  depends  on  the 
total  length  and  may  vary  from  4  to  10  inches.  In  the  welding  of 
complicated  shapes,  such  as  flywheels,  some  castings  may  require 
preheating  at  certain  points  to  produce  initial  expansion,  which  will 
be  overcome  as  the  weld  cools.  In  some  cases  the  entire  pieces  must 
be  preheated;  in  others,  after  welding,  the  whole  piece  must  be 
annealed.  This  is  done  by  heating  the  pieces  uniformly,  then  cover- 
ing it  with  sand,  asbestos,  etc.,  and  allowing  it  to  cool  slowly.  In 
welding  cracks  in  plates,  forgings,  or  castings,  the  crack  or  fracture 
should  be  bevelled  entirely  through  within  3V  inch  of  the  bottom. 

In  boiler  work  J-inch  holes  are  sometimes  drilled  just  beyond  the 
crack  to  prevent  further  fracture. 

Welding  with  the  Metallic  Electrode. — The  arc  should  be  kept 
short,  not  over  |-  inch  in  length.  ^The  current  should  not  be  greater 
than  that  indicated  in  the  table  for  the  electrode.  Excessive  current 
burnt  or  porous  metal  to  be  deposited.  The  arc  should  be  kept 
constant  in  length  to  ensure  uniformity  in  the  metal  deposited.  In 
welding  a  seam  the  electrode  should  be  moved  with  a  zigzag  or  gyra- 
tory motion :  the  motion  must  be  an  advancing  one  along  the  seam. 
The  metal  will  adhere  only  to  the  surface  of  the  work  actually  played 
on  by  the  arc,  so  care  must  be  taken  to  bring  the  arc  in  contact  with 
the  whole  surface  to  be  welded.  Be  sure  that  the  electrode  is  con- 
neoted  to  the  negative  terminal.  If  the  polarity  is  reversed  the 
arc  will  be  more  difficult  to  maintain,  the  electrode  will  not  be  as 
good  as  it  should  be.  In  starting  the  arc,  the  electrode  should  be 
just  touched  to  the  work,  and  withdrawn  immediately  to  the  required 
distance.  If  the  electrode  is  held  too  long  in  contact  it  will  not  work ; 
in  this  case  the  relay,  if  adjusted  properly,  will  operate  opening  the 
circuit,  after  which  the  electrode  can  be  knocked  loose. 

In  welding,  be  sure  that  the  arc  plays  over  the  entire  surface  of 
the  joint.  The  metal  of  the  work  is  fused  by  direct  impact  of  the 
arc ;  if  the  molten  metal  merely  runs  ahead  of  the  arc,  over  the  solid 
metal  of  the  work,  it  will  not  result  in  a  weld.  The  metallic  electrode 
used  is  generally  from  14  to  18  inches  long.  It  may  be  gripped  in  the 
holder,  either  at  one  end  or  in  the  middle  as  required  by  skill  of  the 
operator  or  the  nature  of  the  work.  The  operation  of  welding  over- 
head is  the  same  as  in  normal  welding.  The  difficulty  largely  lies 
in  the  holding  of  the  electrode  steady  in  the  cramped  position 

15 


226  MODERN  METHODS  OF  WELDING 

usually  required.  If  the  arc  length  is  kept  constant  the  metal  will 
be  successfully  deposited;  practice  is  required  to  accomplish  this. 
The  appearance  of  an  over  weld  is  sometimes  marred  by  drops  of 
metal  projecting,  or  by  uneven  thickness  of  the  deposited  metal, 
but  this  can  be  overcome  by  proper  manipulation  of  the  electrode. 
A  rest  for  the  arm  will  sometimes  assist  the  operator  to  hold  the 
electrode  steady. 

The  Use  of  the  Carbon  Electrode. — The  holder  should  grip  the 
electrode  from  4  to  5  inches  from  the  end,  the  electrode  for  ordinary 
work  to  be  tapered  to  a  blunt  point  at  the  working  end.  These 
carbon  electrodes  are  specially  made  from  a  superior  grade  of  pure 
graphite.  They  are  stocked  in  three  sizes — f  inch,  £  inch,  and 
|  inch  diameter — and  12  to  24  inches  long.  To  deposit  metal 
with  the  carbon  electrode,  the  arc  is  struck  as  above,  but  it 
is  not  held  long  enough  in  one  place  to  melt  through.  A  pool 
of  molten  metal  is  established,  a  melting-rod  of  metal  is  fed 
into  the  arc  melted  down  in  the  work.  It  should  all  be  heated 
thoroughly  to  ensure  complete  union  before  more  metal  is  added. 
Since  a  heavier  current  can  be  used  with  the  carbon  electrode 
than  with  fche  metallic,  faster  work  can  be  done  in  depositing 
metal.  The  quality  of  the  weld  is  not  quite  so  good,  however,  as 
when  the  metallic  electrode  is  used.  However,  for  filling  holes  in 
castings, burning  up  worn  spots,  etc.,  the  carbon  weld  is  satisfactory 
and  should  be  used.  Owing  to  the  temperature  and  the  large 
amount  of  heat  liberated  when  using  the  carbon  electrode,  the  elec- 
trode holder  is  liable  to  become  very  hot,  and,  under  some  conditions, 
melt  away  at  the  end.  When  the  holder  begins  to  get  hot  it  should 
be  plunged  in  the  receptacle  of  water  kept  conveniently  near  the 
operator. 


CHAPTER   XXXV 
SPOT  WELDING 

SPOT  electric  welding  is  the  process  whereby  two  pieces  of  metal 
are  united  by  heating  until  they  reach  a  semi-molten  or  plastic 
stage,  when  they  can  easily  be  forced  to  cohere  or  weld  by  the  appli- 
cation of  pressure.  The  complete  cohesion  of  the  heated  molecules 
makes  the  two  pieces  of  metal  practically  solid  where  they  are 
forced  together.  It  is  necessary  that  the  area  to  be  welded  should, 
at  the  start,  be  brought  into  more  intimate  contact  than  the  sur- 
rounding areas,  in  order  that  the  current  may  be  properly  localised, 
and  the  heat  generated  in  the  region  where  it  is  needed. 

Some  of  the  advantages  of  spot  welding  are  that  the  weld  is 
softened  or  changed  in  its  texture  after  welding  by  the  application 
of  considerable  heat,  and  for  this  reason  it  can  be  extensively  used 
in  the  manufacture  of  stoves  or  other  articles  subject  to  high  heat, 
where  even  brazing  could  not  stand  up.     There  is  no  noise  in  con- 
nection with  the  operation,  no  dirt,  smoke,  or  wasted  heat.     The 
current  is  only  on  for  a  brief  period  of  the  time  required  to  heat  the 
two  sheets  of  metal  at  the  point  of  the  weld,  and  as  soon  as  the 
welding  is  completed  all  expense  of  current  ceases  immediately. 
Owing  to  the  way  the  metal  is  forced  together,  no  oxidation  can  take 
({ place  on  the  abutting  surfaces ;  therefore,  no  welding  compound 
or  deoxidiser  of  any  kind  is  necessary.     First  the  stock  must  be 
cold  rolled,  hot  pickled,  or  sand-blasted  to  remove  all  scale  or  dirt, 
I  which  acts  as  an  insulator  and  cuts  down  the  capacity  of  any  spot- 
welding  machine.     The  welding  machine  is  always  ready  to  make 
[   a  joint  at  the  will  of  the  operator;  yet,  as  soon  as  the  welding  has 
I  been  completed,  the  machine  is  practically  dead,  and  the  current 
i  expense  is  stopped  until  the  next  operation.    "The  metal  is  in  full 
view  of  the  operator  at  all  times,  and  no  smoked  glasses  or  goggles 
are  required. 

The  sheets  to  be  welded  must  be  perfectly  flat  and  in  good  con- 
tact at  the  surface  to  be  welded,  so  that  no  great  mechanical  pres- 
sure is  required  to  flatten  down  any  bulges  or  dents  to  bring  the  two 
plates  of  stock  into  good  contact  directly  under  the  die-points. 

227 


228  MODERN  METHODS  OF  WELDING 

The  stock  must  not  surround  the  lower  horn  in  any  way  like  a 
cylinder  or  a  rectangular  box,  as  would  be  the  case  in  welding  the 
seam-side  of  a  can  or  pipe.  These  conditions  are  not  to  be  interpreted 
as  meaning  that  no  spot  welding  can  be  done  unless  they  are  abso- 
lutely followed,  but  merely  to  give  a  basis  on  which  the  ratings  tire 
calculated.  If  any  of  these  conditions  are  violated — which  is  often 
necessary,  especially  the  last  one — it  will  still  be  possible  to  spot 
weld,  but  the  capacity  of  the  machine  will  be  cut  down.  The  cut- 
down  of  the  capacity  as  outlined  (by  the  stock  not  surrounding  the 
lower  horn)  is  due  to  the  self-induction  effect  of  the  metal,  which 
tends  to  choke  back  the  main  current  and  in  this  way  cuts  down 
the  welding  effect  at  the  die-points.  This  is  lost  energy,  as  the 
amount  of  current  choked  back  is  not  used  in  any  way. 

The  theory  of  this  choking  back  would  be  too  lengthy  to  explain 
in  full,  but,  to  give  a  brief  analogy,  it  might  be  compared  to  the  back- 
pressure effect  on  a  petrol  engine  in  a  motor-boat,  where  the  ex- 
haust is  located  under  water  and  the  power  of  the  engine  is  reduced 
owing  to  the  back-pressure  caused  by  the  water  pushing  against 
the  exhaust  gases.  This  induction  effect,  so  called,  is  only  present 
in  welding  iron  and  steel,  no  such  effect  being  experienced  with 
brass. 

Light  gauges  of  sheet  metal  can  be  welded  to  heavy  gauges  or 
solid  bars  of  steel  if  the  light  metal  is  not  greater  than  the  rated 
single  sheet  capacity  of  the  machine.  Soft  steel  and  iron  form  the 
best  welding  materials  in  sheet  metals,  although  it  is  possible  also 
to  weld  sheet  iron  or  steel  to  malleable  iron  castings  of  a  good 
quality.  Galvanised  iron  can  also  be  welded  successfully,  although 
it  takes  a  slightly  longer  time  than  clear  iron  and  steel  stock  in 
order  to  burn  off  the  zinc  coating  before  the  weld  can  be  made. 
Contrary  to  common  opinion,  the  metal  at  the  point  of  the  weld 
is  not  made  susceptible  to  rust  by  burning  of  this  zinc,  since  by  some 
electro -chemical  action  it  has  been  found  that  the  spots  directly 
under  each  die-point  and  also  around  the  point  of  the  weld  between 
the  sheets  are  covered  with  a  thin  volume  of  zinc  oxide  after  the 
weld  has  taken  place,  which  acts  also  as  a  rust-preventative  to  a 
very  noticeable  degree. 

On  spot-welded  articles  used  in  practice  for  some  time,  such  as 
galvanised  road  culverts,  refrigerator-racks  and  pans,  rain  gutters, 
buckets, etc.,  it  has  been  found  that  no  trace  of  rust  has  appeared  on 
the  spot  welds  from  their  exposure  to  ordinary  conditions.  Extra 
light  gauges  of  galvanised  iron  below  No.  28  B.  and  S.  cannot  be 
successfully  welded,  owing  to  the  fact  that  so  little  of  the  iron  is  left 


SPOT  WELDING  229 

after  the  zinc  has  been  burnt  off  that  the  metal  is  very  apt  to  burn 
through  and  leave  a  hole  through  the  sheets.  Tinned  sheet  iron 
or  steel  makes  an  ideal  metal,  giving  great  strength  at  the  weld, 
but  the  stock  will  be  discoloured  at  this  point  over  the  area  covered 
by  the  die-point  in  operation.  Sheet  brass  can  be  welded  to  brass 
or  steel  if  it  contains  not  more  than  60  per  cent,  copper.  It  is  not 
practicable  to  attempt  to  weld  any  bronze  or  alloy  containing  a  higher 
percentage  of  copper  than  this,  as  no  great  strength  can  be  obtained 
Another  class  of  work  which  can  be  handled  to  good  advantage  on 
a  spot-welder,  although  it  is  not  strictly  spot  welding,  is  the  con- 
struction of  wire- work  articles. 

This  mesh  welding  of  two  crossed  wires  is  usually  done  with  the 
same  two  copper  dies  as  are  used  for  spot  welding,  except  that  the 
dies  are  usually  grooved  in  order  to  hold  the  wire  in  the  desired 
position  to  weld.  The  welding  itself  is  quite  as  rapid  as  that  of 
sheet  metal,  but  a  jig  to  hold  the  wire  parts  together  in  the  correct 
position  before  welding  the  joint  is  usually  required  in  order 
to  secure  high  production.  Among  common  wire- work  articles 
assembled  by  this  method  of  welding  will  be  found  lamp-shade 
frames,  oven  racks,  dish  strainers,  waste  baskets,  etc. 

Spot  welding  requires  as  part  of  its  equipment  a  suitable  trans- 
former. The  essentials  for  the  purpose  are : 

(1)  Very  large  currents  at  low  voltages,  the  currents  running  as 
high  as  50,000  to  75,000  amperes,  the  voltage  4  to  15. 

(2)  Different  classes  or  thicknesses  of  metal  having  to  be  welded 
by  the  same  outfit,  it  is  necessary  to  provide  variation  in  voltage  in 
order  to  obtain  suitable  currents  for  the  different  classes  of  work. 

(3)  On  account  of  high  current  it  is  necessary  to  have  the  trans- 
formers as  near  the  work  as  possible  to  avoid  excessive  cost  of  low 
voltage  bus  bars. 

(4)  The  fact  that  the  transformer  is  an  integral  part  of  the  weld- 
ing machine,  and  as  such  may  be  subject  to  very  rough  usage  in 
factories,  blacksmiths'  and  boiler  shops,  etc.,  or  may  even  be  ex- 
posed to  the  weather,  necessitates  particularly  rugged  construction. 

Spot  welding  is  the  method  of  joining  metal  sheets  together  at  any 
desired  point  by  a  spot,  the  size  of  a  rivet,  without  punching  holes 
or  using  rivets.  It  is  done  electrically  by  fusing  or  melting  the  metal 
at  the  point  desired,  at  the  same  instant  applying  sufficient  pressure 
to  force  the  particles  of  molten  metal  together.  The  theory  is  as 
simple  as  its  application.  It  is  a  well-known  principle  that  a  poor 
conductor  of  electricity  will  offer  so  much  resistance  to  the  flow 
of  the  current  that  it  will  heat,  the  degree  of  heat  depending  on  the 


230 


MODERN  METHODS  OF  WELDING 


amount  of  current  and  the  resistance  of  the  conductor.  Copper 
conductors  carry  the  current  with  very  little  resistance.  Place  a 
piece  of  iron  in  the  circuit ;  it  is  not  so  good  a  conductor  as  the  copper, 
and  will  heat.  If  the  volume  of  the  current  is  large,  and  the  iron 
conductor  much  smaller  in  diameter  than  copper,  the  iron  will 


FIG.  112. — PRESCOT  SPOT  WELDER. 

quickly  become  hot  enough  to  melt.  An  incandescent  lamp  offers 
a  good  illustration  of  this  principle :  the  copper  wires  leading  to 
the  lamp  are  good  conductors  and  remain  cool;  the  carbon  fila- 
ment, being  a  poor  conductor,  becomes  white-hot,  and  reaches  a  state 
of  incandescence. 


SPOT  WELDING 


231 


Instruction  for  Working  the  Machine. 

Set  the  regular  handle  to  the  extreme  left-hand  side,  No.  1, 
and  the  double-pole,  double-throw  switch  to  the  left.  Place  the 
work  between  the  copper  die-points  and  close  the  dies  on  the  work. 


FIG.  113. — THIS  is  A  SPECIALLY  GOOD  SAMPLE:  FIRST,  THREE  FLAT  BARS  TO 
CORRUGATED  SHEET;  SECOND,  A  FLAT  PLATE  WELDED  TO  THE  FLAT  BARS 
AND  PLATE;  FOURTH,  BENT  FLAT  BARS  WELDED  TO  CORRUGATED  SHEET, 
FLAT  BARS,  PLATE,  THROUGH  ALL  PIECES. 

This  will  force  the  stock  together.  The  current  is  turned  on  with 
the  switch.  If  the  stock  does  not  heat  rapidly  enough,  turn  the 
regulator-handle  to  the  right,  or  No.  2.  If  not  enough  is  obtained 
at  this  point,  keep  on  until  the  point  is  reached ;  if  enough  heat  is 


FIG.  114. — ONE  PIECE  OF  ANGLE  IRON  TO  FLAT  PLATE.     Two  SroTs. 

not  obtained,  throw  the  double-pole  switch  to  the  right,  and  the 
lever  handle  to  No.  1.  The  maximum  current  is  obtained  when  the 
regulator  is  at  the  right. 

There  is  absolutely  no  danger  of  getting  a  shock  on  the  machine 
between  the  upper  and  lower  dies,  as  can  readily  be  proved  by  plac- 


232 


MODERN  METHODS  OF  WELDING 


ing  the  fingers  through  from  the  upper  to  the  contact  points  and 
turning  on  the  currents. 

The  voltage  is  so  low  that  it  is  impossible  to  feel  anything.  Do 
not  touch  the  wires  leading  from  the  transformer  or  dynamo  to  the 
machine  without  first  opening  the  switch  on  the  wall.  There  is  no 
occasion  for  the  operator  to  touch  these  wires  in  anyway  after  the 
machine  has  been  connected  up. 

Figs.  113,  114,  and  115  are  samples  of  spot  welding. 

There  is  a  limit  to  the  thickness  of  sheet  metal  which  it  is 
commercially  practicable  to  spot  weld,  owing  to  two  causes  : 

First,  the  fact  that  the  copper  rods  which  conduct  the  electric 
current  can  only  carry  a  certain  quantity  of  current  without  exces- 
sive heating.  When  sufficient  current  is  carried  over  these  copper 
rods  or  die-points  to  bring  the  heavy  bodies  of  metal  up  to  the  weld- 


FIG.  115. — THREE  PIECES  OF  ROUND  IRON  WELDED  TO  AN  ANGLE  IRON. 

GOOD  TEST. 

ing  temperature,  the  copper  rods  will  become  hot ;  then  they  soften, 
and  the  points  will  wear  away  quite  rapidly. 

Secondly,  it  being  necessary  to  have  two  pieces  of  sheet  steel 
touching  each  other  at  the  point  where  the  weld  is  made,  with  very 
heavy  stock  a  slight  kink  or  buckling  of  the  metal  will  prevent  the 
flat  surfaces  from  touching  each  other  and  making  good  contact. 
Light  gauges  of  sheet  steel  can  be  welded  to  heavy  gauges  or  to  solid 
bars  of  steel.  It  is  not  possible  to  weld  two  pieces  of  cast  iron,  owing 
to  the  crystalline  structure  of  the  metal.  Sheet  steel  can  be  welded 
to  cast  iron,  but  can  easily  be  pulled  apart.  The  sheet  tears  out 
small  particles  of  cast  iron.  Galvanised  iron  can  be  welded,  although 
it  will  burn  off  the  zinc  somewhat  where  the  weld  is  made.  The 
author  does  not  advise  the  welding  of  light  galvanised  iron  above 
2t-gauge,  as  there  is  no  body  of  metal  to  work  on.  By  the  time  the 
weld  is  done  the  zinc  is  burnt  off  and  there  is  nothing  left.  Sheet 
brass  can  be  welded  to  sheet  brass  or  sheet  steel.  There  is  a  little 


SPOT  WELDING  233 

knack  in  welding  work  of  this  kind,  and  it  may  take  a  bit  of  experi- 
menting to  get  the  right  heat  and  pressure. 

Some  grades  of  sheet  aluminium  can  be  spot  welded,  although  it- 
will  leave  a  slightly  roughened  surface  where  the  die-points  come 
together.  It  is  more  difficult  to  weld  sheet  copper  to  sheet  copper, 
as  this  metal  is  such  a  good  conductor  of  the  electric  current  that 
there  is  practically  no  resistance  offered  by  the  metal.  Rivets  of 
any  size  can  be  heated  after  the  rivet  has  been  set  in  the  rivet- 
hole,  and  headed  and  pressed  in  place  at  one  operation  by  use  of  the 
welder.  This  process  can  be  used  to  advantage  in  many  cases. 
Heat  has  no  effect  on  the  electric  weld.  For  this  reason  the  process 
is  largely  used  by  stove  manufacturers  in  making  sheet-steel  ranges, 
and  for  similar  work. 

To  facilitate  the  welding  of  awkwardly  shaped  articles  the  bottom 
stake  may  be  swivelled  and  raised  or  lowered.  With  such  a  com- 
bination it  is  practicable  so  to  arrange  the  stakes  that  the  most 
awkwardly  shaped  articles  can  be  handled.  The  welder  is  foot- 
operated,  and  no  skilled  labour  is  required.  Foot  pressure  on  the 
pedal  brings  down  the  top  electrode  towards  the  bottom  electrode, 
pinching  between  them  the  articles  to  be  welded,  which  are  held 
there  by  the  operator.  The  same  downward  movement  of  the  pedal 
switches  on  the  welding  current.  After  welding  temperature  is 
reached — judged  by  the  colour — further  pressure  on  the  pedal  trips 
the  switch  and  applies  pressure  to  force  the  heated  metal  into 
welding.  The  pedal  is  made  reversible,  so  that  the  welder  may  be 
operated  by  either  right  or  left  foot.  The  tips  are  made  of  copper 
and  are  water-cooled,  with  a  constant  flow  of  water.  The  system 
of  cooling  is  so  efficient  that  the  tips  may  be  touched  by  hand 
immediately  after  welding.  Usually  the  tips  last  for  a  few  weeks' 
constant  use.  They  are  easily  and  cheaply  replaced. 

Operating  Instructions.  —  Select  the  pieces  to  be  united,  range 
them  together  in  the  required  position,  just  as  they  will  be  when 
welded,  and  clamp  them  thus  between  the  electrode  tips.  This  is 
done  by  holding  the  pieces  on  the  bottom  electrode  until  the  top  elec- 
trode has  been  brought  down  by  depressing  the  foot-lever.  Directly 
the  pieces  are  clamped  between  the  electrodes,  they  become  white- 
hot  at  the  points  where  the  electrode  tips  make  contact;  and  the 
pressure  between  the  surfaces,  maintained  by  the  foot-pedal,  forces 
the  metal  to  unite  and  forms  a  weld.  The  metal  should  be  as  free 
a*  pDSsible  from  rust,  scale,  dirt,  or  other  foreign  matter  likely  to 
hinder  the  passage  of  the  welding  current.  No  preparation  is  neces 
sary  unless  the  metal  is  very  dirty,  in  which  case  it  will  be  economical 


234  MODERN  METHODS  OF  WELDING 

to  clean  it,  since  less  current  will  be  required.  The  time  taken  to 
weld  varies  from  a  fraction  of  a  second  to  perhaps  one  second.  No 
definite  rule  can  be  given  that  will  decide  all  cases.  It  depends  on 
the  thickness  of  the  metal,  its  freedom  from  dirt,  the  position  of  the 
plug  in  the  plug-box,  and  the  diameter  of  the  spot  weld  made. 
A  few  hours'  experimenting  is  generally  sufficient  to  teach  the  average 
operator.  The  plug  should  be  in  No.  1  hole  when  welding  the 
thickest  material,  in  No.  4  for  the  thinnest.  The  shape  of  the  elec 
trode  tip  decides  the  diameter  of  the  spot.  If  a  small  spot  be 
required,  the  tips  must  be  reduced  at  the  tip ;  if  a  larger  spot,  the 
tips  must  be  flattened. 

Adjustments,  Tips. — The  electrode  tips  will  require  to  be  filed 
from  time  to  time,  to  remove  any  metal  which  may  adhere  to  them . 
Each  tip  is  quite  easily  removable  after  loosening  with  a  spanner. 
Care  should  be  taken  not  to  turn  the  tip  completely  round,  as  one 
would  a  nut.  Just  move  it  from  left  to  right  a  few  times,  when  it  will 
be  loosened  and  may  easily  be  removed. 

Three  types  of  electrode  tips  are  made : 

(1)  Concentric — that  is,  with  welding  point  exactly  in  the  middle 
of  the  electrode. 

(2)  Eccentric — that  is,  the  welding  point  a  little  out  of  centre. 

(3)  Flat — that  is,  no  welding  point  at  all. 

The  concentric  type  is  most  often  used,  but  it  demands  a  maxi- 
mum amount  of  clearance  around  the  weld.  For  welding  in  corners 
and  places  where  there  is  little  room,  the  eccentric  is  used.  The 
flat  type  may  be  used  with  either  a  concentric  or  eccentric  tip,  but 
it  is  only  used  when  it  is  desired  to  avoid,  on  one  side,  the  little 
indentation  made  by  the  pointed  electrodes.  All  these  tips  are 
interchangeable,  suitable  for  either  top  or  bottom  stakes. 

Pressure  while  Welding. — One  of  the  most  important  points  to 
remember  is  the  necessity  of  having  a  fair  pressure  between  the  sur- 
faces to  be  welded  before  th-3  current  is  switched  on  by  closing  the 
switch  at  the  back  of  the  welder.  This  can  easily  be  arranged  for 
by  moving  the  top  or  bridge  of  the  switch  up  and  down  the  rod  on 
which  it  is  mounted,  adjusting  so  that  the  electrode  tips  are  forced 
well  together  before  the  switch  closes.  Care  must  be  taken  to 
see  that  the  electrode  tips  are  directly  in  line  when  touching.  If 
one  is  a  little  to  the  side  of  the  other,  the  weld  is  likely  to  be  burnt. 
Directly  the  article  to  be  welded  is  clamped  between  the  electrode?, 
the  secondary  circuit  is  closed,  but  no  current  flows  until  sufficient 
pressure  has  been  set  up  by  the  foot-pedal  to  close  the  primary  switch 
at  the  back  of  the  welder.  Closing  the  secondary  circuit  before  the 


SPOT  WELDING  235 

primary  ensures  a  steady  flow  of  current  through  the  point  of  the 
weld,  free  from  sparking. 

Switch. — This  is  fitted  at  the  back  of  the  welder  and  should  be 
inspected  from  time  to  time  to  ensure  the  points  of  contact  being 
kept  clean. 

Hinge. — To  permit  the  top  arm  to  move  down  easily  when  the 
foot-pedal  is  depressed,  while  yet  maintaining  good  electrical  con- 
tact, it  is  carried  in  a  special  hinge.  The  arm  rocks  up  and  down 
on  ball-bearings,  and  electrical  contact  is  ensured  by  two  discs, 
which  are  a  sliding  fit  in  the  secondary  casting,  and  are  pressed  up 
against  the  top  arm  by  the  springs  under  the  nut-washers  on  each 
side.  These  nuts  may  require  tightening  from  time  to  time,  so  as 
to  keep  the  contact  discs  in  close  contact  with  the  top  arm.  Great 
care  must  be  taken  not  to  make  them  too  tight,  or  excessive  friction 
will  be  set  up  and  the  faces  will  be  scored.  No  lubricant  must  be 
used.  Should  the  faces  at  any  time  become  scored,  take  the  hinge 
apart,  smooth  the  faces,  and  polish  with  metal  polish.  The  ball- 
bearings require  no  attention. 


CHAPTER  XXXVI 
ELECTRIC  BUTT  WELDING 

ELECTRIC  butt  welding  is  a  process  wherein  two  pieces  of  metal  are 
united  by  the  cohesion  of  their  molecules,  induced  by  the  application 
of  pressure  when  they  are  in  a  plastic  or  molten  stage  through  being 
heated  by  some  process.  In  the  process  of  electric  welding  the  heat 
is  induced  by  passing  a  large  volume  of  electric  current  at  a  low 
pressure  through  the  two  surfaces  of  the  pieces  to  be  welded,  the 
heating  effect  in  any  electrical  circuit  being  evoked  by  the  resistance 
of  the  metal  to  the  flow  of  the  current.  When  the  point  between 
the  abutting  ends,  which  has  the  highest  resistance  in  the  circuit 
and  therefore  the  highest  heat,  has  reached  the  proper  welding 
temperature,  the  current  is  turned  off  and  the  pressure  applied 
mechanically  to  force  the  molten  ends  together,  thereby  producing 
a  weld. 

Butt- welding  machines  are  designed  for  the  manufacturer  who 
has  a  large  quantity  of  this  kind  of  work  to  do,  where  there  are  many 
pieces  of  one  kind  to  weld.  They  are  not  intended  to  replace  the 
blacksmith  for  general  repair  work  where  there  are  a  few  pieces 
of  various  sizes  to  be  welded.  It  is  purely  a  production  proposition 
for  a  volume  of  work  with  a  minimum  of  cost. 

In  butt  welding  the  two  pieces  of  metal  are  placed  in  the  clamp- 
ing jaws  of  the  machine  with  a  proportion  of  the  ends  extending 
beyond  the  jaws.  The  electric  current  is  turned  on  by  means  of  a 
switch,  and  the  abutting  ends  of  the  metal  instantly  begin  to  heat. 
The  operator  quickly  learns  to  judge  by  observation  when  the  weld- 
ing temperature  is  reached.  When  he  sees  that  the  metal  is  hot 
enough,  he  applies  the  pressure  and  forces  the  two  metal  ends  of  the 
pieces  into  each  other,  at  the  same  time  turning  off  the  current,  and 
the  weld  is  made.  The  metal  is  in  full  view  of  the  operator  all  the 
time,  instead  of  being  hidden  by  the  coal  and  flame  in  a  forge  fire. 
No  smoked  glasses  or  goggles  are  needed  any  more  than  they  are  by 
the  blacksmith.  There  is  no  scarfing  to  be  done,  and  owing  to  the 
way  the  metal  is  forced  together,  there  is  no  oxidation  such  as  there 
would  be  in  the  open  fire.  Consequently,  no  welding  compound  is 
necessary.  In  a  forge  fire  a  thin  film  of  oxide  forms  on  the  metal, 

236 


ELECTRIC  BUTT  WELDING  237 

which  must  be  removed  by  a  welding  compound  from  the  two  sur- 
faces to  be  joined  before  a  good  weld  can  be  made. 

With  electric  welds  the  heat  is  first  developed  in  the  centre  of 
the  metal.  In  consequence,  it  is  welded  there  as  perfectly  as  the 
surface.  When  welding  electrically,  little  energy  or  heat  is  wasted 
in  heating  more  of  the  material  on  either  side  of  the  weld.  The 
operator  has  complete  control  of  the  electric  current  by  means  of  his 
current  regulator  and  switch.  He  can  quickly  obtain  anv  heat 
desired,  from  a  dull  red  to  the  melting-point  of  the  metal.  The 
instant  the  weld  is  made  the  expense  for  current  stops.  Owing  to 
the  low  voltage  employed  across  the  work  itself  there  is  not  the 
slightest  danger  of  injury  to  the  operator.  He  cannot  even  feel  the 
current  if  he  should  come  in  contact  with  it  across  the  dies.  The 
parts  to  be  welded  can  be  kept  in  fairly  close  alignment  by  the 
clamping  of  the  jaws,  which  can  be  given  almost  any  shape  desired 
to  hold  the  work.  The  current  has  no  effect  on  the  welded  metal,  its 
action  being  to  heat  the  metal.  The  copper  clamping  dies  are  good 
conductors,  and  a  bar  of  iron,  being  comparatively  a  poor  conductor, 
when  placed  between  the  clamping  dies  of  the  welder  becomes 
heated  in  attempting  to  carry  the  large  volume  of  current.  The 
degree  of  heat  depending  upon  the  amount  of  current  and  resistance 
of  the  conductor  when  the  ends  of  the  two  pieces  of  bar  are  brought 
together,  this  is  the  point  of  the  greatest  resistance  in  the  electric 
circuit,  and  the  abutting  ends  heat  most  rapidly. 

Production  will  depend  largely  on  the  operator,  the  size  and 
shape  of  the  piece  to  be  welded,  and  the  kind  of  machine  used. 
There  is  a  wide  range  in  the  time  between  the  heavy  pieces  and  the 
light  pieces  which  can  be  handled  rapidly  and  easily.  Some  of  the 
smaller  machines  deal  with  several  thousands  of  pieces  a  day,  and 
to  get  the  maximum  output  the  best  machines  should  be  adopted. 
The  welding  machine  can  be  used  on  one  phase  of  a  three-phase 
system,  but  cannot  be  connected  to  more  than  one  phase  of  a  three- 
phase  circuit.  Direct  current  cannot  be  used,  because  there  is  no 
way  of  reducing  the  voltage  without  interposing  resistance,  which 
uses  up  the  power.  The  voltage  used  at  the  weld  is  from  1  to  15, 
depending  on  the  size  of  the  welding  machine.  To  obtain  this 
low  voltage  or  pressure,  a  special  transformer  inside  the  machine 
reduces  the  power  line  voltage  down  to  the  range.  It  is  like 
reducing  steam  pressure  from  100  to  10  pounds. 

The  welding  transformer  which  produces  the  heavy  current  across 
the  work  is  supported  with  the  frame.  Single-phase  alternating 
current  is  taken  from  a  generator,  or  power  circuit,  and  is  stepped 


238  MODERN  METHODS  OF  WELDING 

down  by  the  transformer  to  a  low  potential  of  from  1  to  15  volts.  The 
secondary  winding  of  the  transformer  is  connected  to  the  platens, 
and  the  current  travels  through  the  platens,  clamps,  and  metals 
to  be  welded,  thereby  completing  an  electric  circuit.  Since  the 
current  value  rises  as  the  potential  falls  in  the  secondary  circuit, 
and  since  also  the  heating  effect  across  the  work  is  directly  propor- 
tioned to  the  current  value,  it  is  easily  seen  why  a  transformer  is 
necessary  to  produce  a  heavy  current  by  lowering  the  time  potential. 
Owing  to  the  intermittent  character  of  the  load,  there  is  no  standard 
rating  for  welder  transformers.  Different  makers  will  give  entirely 
different  ratings  for  their  machines,  and  not  infrequently  make 
misleading  statements  regarding  the  current  used.  Regardless  of 
the  rating  in  k.w.  capacity,  there  can  be  very  little  difference  in  the 
actual  amount  of  current  consumed  unless  an  exceptionally  bad 
transformer  design  is  used.  To  heat  a  given  size  stock  to  the 
welding  temperature  in  a  given  time  requires  approximately  an 
invariable  amount  of  current. 

The  following  illustration  shows  a  machine  for  welding  tool  steel. 
In  any  tool  welding  there  are  different  kinds  of  welds  to  be  made, 
which  require  different  classes  of  dies  and  two  different  types  of 
machines.  We  will  first  deal  with  the  class  of  work  which  comes 
under  reamers,  milling  and  key-way  cutters  with  taper  shanks, 
and  other  similar  make-up.  The  high  speed  and  the  carbon  steel 
pieces  should  be  prepared  to  secure  the  best  results  on  a  production 
basis.  When  making  this  style  of  tool  the  dies  should  be  specially 
prepared  to  do  the  work.  Since  the  high-speed  steel  has  a  higher 
resistance  than  the  carbon  steel  it  has  a  great  tendency  to  reach  the 
plastic  stage  of  heat  sooner  than  the  latter.  For  this  reason  it  should 
have  a  shorter  projection  beyond  the  dies  to  secure  still  greater 
cooling  effect  and  to  retard  its  heating  as  much  as  possible. 

Thorough  tests  have  been  made  on  the  strength  of  electrically 
welded  bars  which  prove  that  they  are  almost  as  strong  at  the  welded 
joint  as  at  any  other  cross-section  of  the  metal.  When  welding  in  a 
forge,  the  outer  surface  is  heated  first,  and  the  inner  part  does  not 
very  often  reach  welding  heat,  the  result  being  an  imperfect  weld. 
The  only  preparation  of  the  stock  necessary  for  this  process  is  that, 
when  it  is  rusty  or  covered  with  blue  scale,  the  rust  and  scale 
should  be  removed  sufficiently  to  give  good  contact  of  clean  metal 
at  the  gripping  dies,  as  both  scale  and  rust  are  poor  conductors. 

The  butt-welding  process  is  applicable  to  the  welding  of  pieces 
having  practically  the  same  cross-section  at  the  joint.  A  very  few 
seconds  after  the  current  is  turned  on  in  the  welder,  the  metal  reaches 


ELECTRIC  BUTT  WELDING 


239 


a  white  heat,  and  is  in  a  partially  molten  state.     By  means  of  heavy 
pressure  the  ends  of  the  metal  are  forced  into  each  other  in  this  semi- 


FIG.  11C. — BUTT- WELDING  TOOL  STEEL  TO  MILD  STEEL  BARS. 

fluid  condition,  extruding  all  burnt  metal,  thus  making  a  homogene- 
ous mass  and  a  perfect  weld.  A  projection  or  fin  will  be  raised  where 
the  ends  come  together,  by  the  squeezing  out  of  the  burnt  metal, 


240  MODERN  METHODS  OF  WELDING 

which  may  be  very  slight  on  an  "upset,"  or  quite  a  fin  may  be 
raised  in  a  flash  weld.     Both  are  shown  below. 

Butt  Electric  Welding  Process. — The  parts  to  be  welded  are 
brought  into  contact  under  pressure  and  then  a  current  of  high 
amperage  under  low  voltage  is  passed  from  one  part  through  the 
joint  to  the  other  part.  Because  of  the  high  resistance  at  the  con- 
tact areas,  the  metal  at  the  joint  is  quickly  brought  to  a  welding 
heat,  when  the  plasticity  of  the  metal  allows  the  pressure  to  cause 
movements  of  the  two  parts  towards  each  other.  Under  the  combined 
temperature  and  pressure  the  parts  are  welded,  much  as  welding 
is  done  under  the  blacksmith's  hammer — perhaps,  above  all,  in 
that  the  heating  and  welding  operations  are  performed  practically 
at  the  same  time  and  almost  instantaneously.  As  soon  as  the  weld- 
ing heat  is  reached  the  welding  is  immediately  effected.  In  the 
lighter  kind  of  work  the  rapidity  with  which  this  heat  is  attained  is 


FIG.  117. — BUTT  WELD.     RIGHT,  FLASH  WELD;  LEFT,  UPSET  WELD. 

quite  remarkable.  Although  the  process  is  not  applicable  to  every 
form  of  welding,  yet  the  sphere  of  its  utility  is  very  wide,  and 
the  quality  of  the  work  effected  by  it  is  unquestionably  good. 
It  is  necessary  for  its  effective  operation  to  have  at  command  heavy 
flows  of  current,  but,  on  the  other  hand,  the  voltage  is  very  low. 
In  some  cases  as  low  an  electromotive  force  as  half  a  volt  is  all  that 
is  required.  In  actual  practice  from  4  to  6  volts  is  about  the  highest 
pressure  worked  with.  The  temperature  of  the  metal  to  be  welded 
is  raised  simply  by  a  very  heavy  current  flowing  through  a  restricted 
area.  The  British  Insulated  and  Helsby  Cables,  Ltd.,  make  a  large 
variety  of  these  machines  for  electric  welding  on  the  resistance 
system.  The  electric  arrangements  involved  in  all  machines  are 
fundamentally  the  same  as  those  employed  in  all  systems  of  resist- 
ance welding — that  is  to  say,  each  machine  embodies  a  transformer, 
wound  so  as  to  perform  the  particular  work  desired  under  the  con- 
ditions of  voltage  and  periodicity  of  the  supply  current  available. 
The  secondary  coil  of  the  transformer  consists  of  a  single  convo- 
lution, having  a  large  cross-section  of  copper,  which  terminates  ex- 


ELECTRIC  BUTT  WELDING 


241 


ternally  in  the  two  electrodes,  which  are  of  various  forms.  The  pieces 
to  be  welded  are  brought  between  these  two  electrodes,  thus  com- 
pleting the  electrical  circuit  of  the  secondary  coil,  so  th  at  when  the 
primary  circuit  is  closed  a  heavy  current  flows  in  the  former,  as  the 
resistance  to  the  flow  of  that  current  is  practically  all  centred  in  the 
surfaces  in  contact.  Since  the  ohmii)  resistance  of  the  secondary 


FIG.  118.— BUTT  WELDER  FOB  TOOL  STEEL  AND  OTHER  WORK. 

winding  is  comparatively  negligible,  great  heat  is  developed  between 
the  electrodes,  and  the  material  between  them  is  quickly  brought  up 
to  a  welding  temperature. 

Attention  may  be  drawn  to  the  various  types  of  butt-welding 
machines  to  suit  different  purposes:  (1)  Welders  for  wire  with  auto- 
matic upsetting  gear  for  uniform  section  iron,  steel,  or  non-ferrous 

IB 


242 


MODERN  METHODS  OF  WELDING 


metals;  (2)  welders  for  manufacturing  purposes  with  hand  or  auto- 
matic upsetting  gear  for  regular  sections;  (3)  chain  welders. 

Wire  welders  is  the  term  which  applies  to  the  machine  in  No.  1, 
some  capable  of  welding  0-024  diameter.  Larger  machines  of  this 
type  are  able  to  weld  material  up  to  1  inch  square.  The  machines 
in  the  second  category  are  used  for  such  manufacturing  purposes, 
amongst  a  host  of  others,  as  welding  pipe  refrigerator-coils,  milk-can 
rings,  perambulator  rings,  printers'  chases,  fittings  to  casement 


FIG.  119. — BUTT  WELDER  MAKING  CHAINS  AUTOMATICALLY. 

frames,  carriage  and  coach  work  parts,  trellis  work,  coupling  links, 
brake  rigging,  travelling-bag  frames,  low-grade  shanks  on  high-speed 
tools,  drills,  taps,  etc. 

The  chain  welders  form  a  class  by  themselves,  though  the  general 
principles  involved  are  very  much  the  same  as  those  of  other 
machines.  The  manufacture  is  carried  out  from  coils  of  wire  by  two 
machines,  the  first  of  which  bends  the  links  and  threads  them  into  a 
chain,  whilst  the  second  forms  the  welds.  Although  the  first  machine 
is  not  shown  in  this  book,  it  is  necessary  to  describe  it,  since  the 


ELECTRIC.  BUTT  WELDING  243 

complete  process  cannot  be  properly  understood  without  it.  Three 
machines  are  made  which  deal  with  wires  from  ^V  to  TV  inch.  The 
smallest  machine  turns  out  50  to  60  links  per  minute  and  takes 
1  to  2|  horse-power  to  drive  it.  The  middle  size  turns  out  40  to  50 
per  minute,  and  requires  2  to  4  horse-power  to  drive  it.  The  large 
one  makes  from  20  to  30  links  per  minute,  and  the  horse-power 
needed  is  3  to  7.  The  minimum  proportions  of  the  links  made  on 
these  machines  are — length  5  diameters  and  width  3  diameters 
of  wire. 

General  Information. — The  material  to  be  welded  should  be  ground 
or  filed  flat  and  square  at  the  abutting  ends,  otherwise  accurate 
results  cannot  be  obtained.  The  wires  to  be  joined  are  each  gripped 
in  a  vice  and  the  two  ends  projecting  equally;  one  of  the  vices  is 
movable  and  the  other  fixed.  While  the  machine  is  being  set  up  a 
spring  pressure  is  taken  up  by  a  pawl  engaging  with  a  rack.  While 
welding,  the  pawl  is  disengaged,  and  this  pressure  is  transmitted  to 
the  joint.  As  long  as  the  wires  are  cold  the  side  remains  stationary, 
but  as  soon  as  the  current  is  sent  through  they  soften  and  give  way : 
the  weld  is  jumped  as  soon  as  the  required  temperature  is  reached, 
and  simultaneously  the  current  is  cut  off,  nothing  further  taking 
place. 

The  illustration  on  the  opposite  page  is  of  a  chain  welder,  which 
has  been  described  previously. 


CHAPTER  XXXVII 
ELECTRIC  SEAM  WELDING 

SEAM  welding  is  a  process  of  joining  two  overlapping  edges  of  sheet 
metal  for  their  entire  length  by  perfect  cohesion  of  the  molecules 
of  the  material  itself,  without  the  application  of  any  solder  or  spelter 
between  the  edges  of  the  joint.  In  the  process  of  seam  welding  the 
heat  is  produced  by  passing  a  large  volume  of  electric  current  across 
the  joint  of  the  edges  to  be  welded  by  the  employment  of  a  copper 
roller  on  one  side  of  the  joint,  a  copper  track  or  horn  underneath. 
In  any  electrical  path,  wherever  high  resistance  is  interposed,  heat- 
ing will  result.  The  higher  the  resistance  to  the  current  the  greater 
will  be  the  heating  effect.  In  seam-welding  machines,  since  the 
copper  rollers  and  horn  are  good  conductors,  the  joint  between  the 
edges  of  the  metal  to  be  welded  is  the  point  of  highest  resistance, 
and  it  is  evident  that  the  greatest  heating  effect  will  be  at  this  point. 
As  the  roller  passes  over  the  joint,  heating  the  stock  to  a  plastic 
state  beneath  it,  pressure  is  simultaneously  applied  by  the  springs  on 
the  roller  to  force  the  edges  together  as  fast  as  they  are  heated. 

Since  20-gauge  metal  and  lighter  heats  very  readily,  the  pressure 
and  the  heating  can  be  effected  at  the  same  instant  of  contact  by  the 
roller.  It  is  possible  to  weld  as  fast  as  6  inches  a  second.  The 
only  preparation  necessary  for  seam  welding  is  that  the  stock  must 
be  absolutely  clean — that  is,  free  from  any  traces  of  rust,  scale, 
grease,  or  dirt — if  a  tight,  neat  joint  is  desired.  If  it  is  not  necessary 
for  the  joint  to  be  tight,  the  stock  need  not  be  so  clean,  although 
heavy  rust  and  scale  will  prevent  the  carriage  of  the  full  current, 
the  heating  will  be  affected,  and  the  weld  will  not  be  so  good. 

In  welding  sheet  brass  from  22-  to  30-gauge,  to  secure  a  perfect 
joint  the  metal  should  be  carefully  pickled  and  washed  to  remove  all 
traces  of  grease  and  tarnish,  which  tend  to  prevent  the  passage  of 
the  current  across  the  joint  of  the  edges.  The  metal  should  be 
welded  soon  after  pickling,  as,  no  matter  how  carefully  it  may  have 
been  washed,  oxidation  is  always  sure  to  start  very  shortly  after  the 
brass  has  been  removed  from  the  pickling  acid. 

Steel  to  be  successfully  seam  welded  should  not  have  a  carbon 

244 


ELECTRIC  SEAM  WELDING 


245 


content  of  over  0-15  per  cent.  A  higher  carbon  steel  than  this  has  a 
tendency  to  crystallise  at  the  point  of  the  weld,  owing  to  the  rapid 
cooling  of  the  welded  portion  from  the  surrounding  cold  metal.  After 
welding,  the  joint  will  be  found  to  be  about  one-third  thicker  than  the 
thickness  of  the  metal.  It  is  possible  by  applying  more  pressure  to 
reduce  this  finished  thickness,  but  it  wears  more  on  the  copper  roller 
to  do  so.  In  seam  welding  brass,  a  soft,  annealed  metal  should  be 
used,  for,  although  hard  rolled  brass  can  be  welded,  it  forces  the  two 
edges  together  very  much,  and  the  finished  joint  under  these  con- 
ditions is  almost  twice  the  original  thickness.  With  a  soft,  annealed 


FIG.  120. — ELECTRIC  SEAM -WELDING  MACHINE. 

brass  the  finished  joint  will  not  be  over  a  third  greater  than  the  single 
metal  thickness,  and  by  applying  sufficient  pressure  it  can  be  reduced 
to  not  over  10  per  cent,  thicker. 

The  principal  advantage  of  the  process  of  seam  welding  in  brass 
and  other  non-ferrous  metals  is  that  no  spelter  or  flux  is  required, 
nor  is  there  any  volatilisation  of  the  zinc,  the  metal  itself  furnishing 
its  own  cohesive  properties.  This  allows  of  great  speed  in  production. 
The  great  ability  of  a  seam  welder  to  secure  the  highest  production 
lies,  not  only  in  its  welding  qualities,  but  in  the  adaptation  to  the 
welding  machine  of  a  suitable  jig.  The  jig  holds  the  work  properly, 


246  MODERN  METHODS  OF  WELDING 

and  also  enables  the  operator  to  place  the  piece  in  it  and  remove 
the  same  in  the  shortest  possible  time,  since  the  welding  itself  is 
very  fast  compared  with  any  other  method  of  making  a  continuous 
joint. 

Fig.  120  is  a  photograph  of  a  seam-welding  machine.  The 
operation  is  very  simple,  once  the  machine  is  set  up,  for  any  given 
piece  of  work  for  which  a  special  jig  has  been  built.  After  placing 
the  piece  in  the  jig  and  locking  it  there  securely,  the  operator  de- 
presses the  foot-pedal,  which  throws  in  a  clutch  and  starts  the  copper 
roller  across  the  work.  By  the  proper  setting  of  adjustable  control- 
stops  on  the  control  rod  on  the  top  of  the  machine,  the  current  is 
automatically  turned  on  as  the  rollers  enter  on  to  the  overlapping 
edges  of  the  piece  to  be  welded,  and  is  automatically  turned  off  when 
the  roller  reaches  the  end  of  the  stroke.  Another  stop  reverses  the 
travel  of  the  roller,  bringing  it  back  to  its  starting  position.  The  con- 
trol stop  may  be  adjusted  to  turn  the  current  on  and  off  at  any  point 
along  the  roller,  for  doing  a  seam  shorter  than  the  maximum  of  the 
welding  machine.  The  roller  stroke  may  also  be  shortened  so  that 
a  complete  cycle  of  operations  will  be  accomplished  in  the  shortest 
space  of  time  on  seams  shorter  than  the  maximum  seam  capacity  of 
the  machine.  In  order  to  keep  the  copper  roller  from  overheating 
in  action,  water  is  introduced  through  its  bronze  bearings  on  each 
side.  This  same  water  circulation  passes  also  through  the  under 
copper  horn  or  madrel,  then  through  the  cast  copper  secondary  of  the 
transformer,  so  that  the  machine  can  be  operated  continually— 
twenty-four  hours  a  day  if  desired — without  overheating. 

Most  seam-welding  machines  are  equipped  with  variable-speed 
motors  in  order  to  give  a  range  of  variation  in  roller  travel  speed, 
which  is  necessary  for  different  lengths  and  thicknesses  of  stock. 
They  are  also  equipped  with  a  current  regulator  to  give  fifty  different 
voltages  at  the  copper  roller. 

To  effect  good  sliding  contact  with  copper  track,  several  springs 
are  employed  on  each  side  of  this  slide,  which  carries  the  copper 
rollers.  The  lower  horn  is  bolted  directly  to  the  lower  terminal  of 
the  transformer  secondary.  The  particular  design  in  each  case  will 
depend  upon  the  size  and  the  nature  of  the  work. 


CHAPTER  XXXVIII 
EYE-PROTECTION  IN  IRON  WELDING  OPERATIONS 

IN  welding  operations  three  kinds  of  radiations  must  be  guarded 
against,  one  or  all  of  which  may  be  present  to  an  injurious  degree. 
The  problem  is  to  provide  a  perfectly  safe  filter  that  will  permit  of 
the  greatest  degree  of  visibility,  and  at  the  same  time  will  exclude 
the  infra-red,  or  heat,  rays  and  the  ultra-violet  rays.  Ordinary  glass 
lenses  of  special  colours  or  combinations  of  colours  are  required. 
I  show  the  spectra  of  a  number  of  commercially  available  glasses  and 
combinations  of  these  glasses,  and  a  glance  at  these  charts  will 
show  what  arrangement  of  filter  will  provide  the  best  protection 
against  the  radiations  of  the  welding  arc. 

Radiation  from  an  intensely  heated  solid  or  vapour  may  be 
divided  under  the  headings:  (1)  Invisible  infra-red  rays;  (2)  visible 
light  rays;  (3)  invisible  ultra-violet  rays. 

There  is  no  clear  line  of  demarcation  between  these  divisions, 
as  they  melt  gradually  one  into  the  other  like  the  colours  of  the 
visible  spectrum.  When  the  heated  matter  is  solid,  such  as  the 
filament  of  an  incandescent  lamp,  the  visible  spectrum  is  usually 
continuous — that  is,  without  lines  or  bands,  but  when  it  is  in  the  form 
of  gas  or  vapour,  as  in  the  iron  arc  used  for  welding  operations,  the 
spectrum  is  divided  up  into  bands,  or  is  crossed  by  lines  which  are 
characteristic  of  the  element  heated. 

In  Fig.  121 A  shows  the  continuous  spectrum  made  by  the  light  of 
a  Mazda  lamp  operated  at  normal  voltage,  and  is  the  line  of  sp  act  rum 
made  by  a  disruptive  arc  between  iron  terminals. 

If  A  and  B  (Fig.  121)  were  coloured  they  would  show  all  the  hues 
of  the  prismatic  spectrum  from  red  at  the  left  to  violet  at  the  right, 
as  roughly  indicated  by  the  vertical  dividing  lines.  The  iron  spec- 
trum B  falls  a  little  short  of  the  continuous  spectrum  A  in  the  red, 
but  it  is  more  intense  than  A  in  the  visible  blue  and  violet,  and  it 
also  extends  farther  into  the  ultra-violet.  The  spectrum  B  contains 
many  lines  besides  those  pertaining  to  iron,  principally  those  of 
carbon,  nitrogen,  and  oxygen,  these  elements  being  unavoidable 
components  of  the  electric  spark  discharge.  Inspection  of  A  and  B. 
however,  will  serve  to  indicate  the  extent  and  general  characteristics 

247 


248 


MODERN  METHODS  OF  WELDING 


of  the  visible  light  that  is  emitted  by  highly  treated  iron  vapour 
in  the  process  of  arc  welding. 

The  radiations  under  the  foregoing  three  headings,  although  of 


FIG.  121. — SPECTRUM  OF  A  MAZDA  LAMP;  SPECTRUM  or  IRON  ARC. 

common  origin,  produce  very  diverse  effects  upon  our  senses.  Thus, 
the  infra-red  rays  produce  the  sensation  of  heat  when  they  fall  on  our 
unprotected  skin,  and,  therefore,  special  glasses  are  required  to  pro- 
tect the  operator  from  their  harmful  effects. 


FIG.  122. — PFUND  GOLD  GLASS  GOGGLES. 

For  v  welding  with  acetylene  and  for  light  electric  welding  it 
may  be  necessary  only  to  protect  the  eyes  with  goggles  fitted  with 
suitable  coloured  glasses.  Fig.  122  shows  a  good  form  of  goggles 


EYE-PROTECTION  IN  IRON  WELDING  OPERATIONS     249 


which  are  fitted  with  lenses  of  pfund  gold  glass  to  which  reference 
will  be  made  later. 

Fig.  124  illustrates  the  front  and  back  views  of  a  hand  shield, 
which  is  made  of  light  wood  and  has  a  safety  coloured  glass  window 
in  the  centre.  This  device  is  used  for  medium  weight  electric  welding 
work  which  can  be  done  with  one  hand,  and  it  serves  the  double 
purpose  of  protecting  the  eyes  of  the  operator  and  shielding  his  face 
from  the  heat  ray  sand  the  ultra-violet  radiation  which  would  other- 
wise cause  a  severe  sunburn  effect. 

For  heavy  electric  welding  which  requires  the  use  of  both  hands 
it  is  common  practice  for  the  operator  to  protect  his  eyes  and  neck 


FIG.  123. — A  POPULAR  FORM  or  HELMET  WITH  CIRCULAR  WINDOW. 

with  a  helmet  fitted  with  a  round  or  triangular  window  of  safety 
glass.  These  helmets  are  usually  made  of  some  strong,  light  material 
such  as  vulcanised  fibre  and  are  designed  so  that  they  can  be  slipped 
on  and  off  easily,  the  weight  resting  upon  the  shoulders  of  the  opera- 
tor. A  useful  form  of  helmet  with  a  circular  window  is  shown  in 
Fig.  123.  Front  and  back  views  of  another  form  of  helmet  are  seen 
in  Fig.  125. 

It  therefore  naturally  follows  that  a  much  clearer  definition  of 
an  object  is  obtained  by  combination  of  yellow-green  light  than  by 
red  alone,  or  especially  by  blue  or  violet  light  alone.  The  eye  is 
also  more  sensitive  to  the  yellow  and  green  rays  than  to  the  red  and 


250 


MODERN  METHODS  OF  WELDING 


blue  rays,  or,  in  other  words,  yellow-green  light  has  the  highest 
luminous  efficiency.  This  may  easily  be  verified  by  looking  at  a 
sunlit  landscape  or  fleecy  clouds  in  a  blue  sky  through  plates  of 
different  coloured  glass.  A  glass  of  a  light  amber  colour,  slightly 
tinted  with  green,  will  clearly  bring  out  details  that  are  hardly 
observable  without  the  glass,  and  which  can  be  obscured  entirely 
by  a  blue  or  violet  glass.  It  is  therefore  obvious  that,  in  order  to 

obtain  the  clearest  definition  or 
visibility  with  the  least  amount  of 
glare,  the  selection  of  the  colour  tint 
in  safety  glasses  should  properly  be 
decided  by  an  expert,  but  the  depth 
of  tint,  or,  in  other  words,  the 
amount  of  obscuration,  may  be  best 
determined  by  the  operator  himself 
owing  to  the  individual  difference 
in  visual  acuity  which  will  permit 
one  man  to  see  clearly  through  a 
glass  that  would  be  too  dark  for 
another  man. 

A  proper  selection  of  colour 
tints  can  be  assisted  by  spectro- 
scopic  examination,  and  the  various 
spectra  shown  in  the  accompanying 
photographs  are  presented  with  this 
purpose  in  view. 

Fig.  126  shows  different  spectra 
made  by  transmitting  the  light  of  a 
Mazda  lamp  operated  at  normal 
voltage :  (7,  through  clear  colourless 
glass;  D,  through  ruby  glass. 

The   screen   of   clear   colourless 
glass  in  C  naturally  transmits  all 
FIG.  124. — WELDER'S  HAND  SHIELD,    the  colours  of  the  visible  spectrum, 

extending   from    the   extreme    red 

to  the  extreme  violet  and  penetrating  slightly  into  the  ultra-violet, 
because  the  latter  rays,  although  they  are  not  visible  to  the  eye, 
are  highly  actinic,  and  therefore  affect  the  photographic  plate.  In 
this  case,  however,  we  only  see  just  the  beginning  of  the  ultra-violet 
spectrum,  as  the  glass  plate  and  the  glass  prism  of  the  spectroscope 
absorb  and  cut  off  all  but  a  few  of  the  least  refrangible  ultra-violet 
ravs. 


EYE-PROTECTION  IN  IRON  WELDING  OPERATIONS     251 

The  ruby  glass,  used  as  a  screen  in  D,  transmits  all  the  red  and 
orange  rays  with  a  trace  of  the  yellow,  but  it  absorbs  and  cuts  out 
all  other  colours. 

The  glass  used  in  spectrum  E  is  made  by  the  Pittsburg  Glass 
Company  (Pa.),  and  is  termed  i;  Belgian  pot-yellow  "  glass.  It  cuts 
off  a  little  of  the  red,  transmits  all  the  orange  and  yellow  rays  and  a 
portion  of  the  green,  but  cuts  out  all  the  blue  and  violet. 

The  emerald-green  glass  marked  F  is  seen  to  transmit  all  the 
yellow  and  green,  with  a  considerable  portion  of  the  red  and  orange 
and  also  of  the  blue. 

The  spectrum  made  through  the  cobalt-blue  glass  marked  G, 
shows  the  transmission  of  a  band  of  red  and  a  band  of  yellow- 


FIG.  125. — FRONT  AND  BACK  VIEWS  OF  THIN  SHEET  ALUMINIUM  HELMET  SUP- 
PORTED BY  A  HEAD  BAND  AND  FITTED  WITH  RECTANGULAR  OPENING. 

green,  but  it  is  chiefly  marked  by  its  strong  transmission  of  the  blue 
and  violet,  and  especially  in  its  being  a  little  more  transparent  to 
the  ultra-violet  than  the  colourless  glass  A. 

These  five  glasses  are  samples  taken  from  actual  service,  but  on 
account  of  the  fact  that  all  coloured  glasses  are  subject  to  con- 
siderable variation  in  tint  and  depth  of  colour,  caused  by  differences 
in  chemical  composition,  heat  treatment,  etc.,  the  spectra  shown  in 
Fig.  126  can  be  considered  as  only  generally  representative;  samples 
of  blue  glass,  for  example,  have  been  tested  and  found  to  absorb 
very  much  more  of  the  red,  yellow,  and  green  than  the  sample 
shown  in  G. 

In  H  is  seen  a  representative  spectrum  taken  through  a  noviweld 


252  MODERN  METHODS  OF  WELDING 

glass  (No.  6  grade),  which  presents  an  excellent  colour  combination 
to  secure  clear  definition  with  the  least  amount  of  glare. 

It  is  possible  to  produce  satisfactory  colour  tints  for  welders' 
glasses  by  combining  plates  of  different  coloured  glass.  The  results 
of  some  of  these  combinations  are  shown  in  the  spectra  of  Fig.  127, 
which  were  made  with  the  same  source  of  light  as  those  of  Fig.  126. 

In  Fig.  127  J  shows  the  full  spectrum  through  clear  colourless 
glass  for  comparison,  the  same  as  C  in  Fig.  126. 

In  K  we  see  the  effect  of  combining  yellow  and  blue  glass  (E  and 
G  of  Fig.  126),  which  combination  makes  a  fair  resemblance  to  novi- 
weld, and  is  giving  satisfactory  service  in  certain  work  where  the 
cost  of  noviweld  prohibits  its  use.  The  tint  of  this  combination 


FIG.  126.— SUNDRY  SPECTRA  6. 

E,    Through    "Belgian    pot-yellow    glass";    ^through    emerald-green    glass; 
G,  through  cobalt-blue  glass;  H,  through  No.  6  "  noviweld  "  glass. 

is  inclined  rather  too  much  to  the  red,  and  is  somewhat  weak  in  the 
yellow-green,  but  these  defects  could  be  largely  overcome  by  a  care- 
ful selection  of  the  plates. 

The  spectrum  L  in  Fig.  127  results  from  a  combination  of  ruby 
and  emerald-green  glass  (Dand  F  in  Fig.  126),  which  has  been  found 
satisfactory  for  certain  work  and  is  now  used  extensively. 

The  result  of  combining  ruby  and  blue  (D  and  G  in  Fig.  126)  is 
shown  by  M  in  Fig.  127.  It  was  formerly  used  to  some  extent,  but 
is  now  almost  universally  superseded  by  L. 

The  spectrum  N  was  taken  through  a  single  plate  of  noviweld 
(No.  5  grade),  which  presents  the  elements  of  an  ideal  colour  com- 


EYE-PROTECTION  IN  IRON  WELDING  OPERATIONS     253 

bination,  being  weak  in  the  red  while  transmitting  all  the  orange, 
yellow,  and  green,  but  totally  excluding  the  blue  and  violet. 

The  spectrum  P  was  taken  through  a  piece  of  amber  mica  having 
a  little  darker  tint  than  No.  5  noviweld.  Its  close  resemblance  to 
the  noviweld  spectrum  is  remarkable,  and  if  it  were  possible  to 
procure  a  clear  dark  amber  mica  in  pieces  large  enough  to  be  service- 
able, this  material,  when  protected  from  mechanical  injury  between 
plates  of  plain  clear  glass,  would  closely  rival  the  noviweld.  Clear 
dark  amber  mica  of  uniform  tint  and  even  cleavage  is,  however, 
very  difficult  to  procure,  for  which  reason  there  is  no  probability 
that  it  will  ever  supersede  glass  for  protective  purposes. 

In  selecting  coloured  glasses,  great  care  should  be  taken  to  dis- 


FIG.  127. — SUNDRY  SPECTRA  7. 

card  all  samples  that  show  streaks  or  spots,  as  these  defects  are  liable 
to  produce  eye-strain.  The  glass  should  be  uniform  in  colour  and 
thickness  throughout,  and  the  coloured  plates  should  be  protected 
from  outside  injury  by  a  thin  piece  of  clear  glass  that  can  easily  be 
renewed. 

Having  considered  briefly  the  best  means  for  toning  down  the 
glaring  and  flickering  visible  light  produced  in  the  welding  process, 
we  may  now  direct  some  attention  to  the  infra-red  and  the  ultra- 
violet rays,  which  always  accompany  the  visible  glare. 

When  the  invisible  infra-red  rays  encounter  any  material  which 
they  cannot  penetrate  or  which  is  opaque  to  them,  they  are  absorbed 
and  changed  into  heat.  Hence  they  are  frequently  termed  heat  rays. 
It  is  therefore  very  necessary  to  guard  the  eyes  from  these  rays,  and. 


254 


MODERN  METHODS  OF  WELDING 


r" 


although  they  are  absorbed  to  a  certain  extent  by  ordinary  coloured 
glass,  this  is  not  sufficient  protection  against  any  intense  source. 
There  are,  however,  several  kinds  of  glass  which,  although  fairly 
transparent  to  visible  light,  are  wonderfully  efficient  in  absorbing 
heat. 

Corning  glass  G  124  J  is  one  of  those  which,  while  it  transmits 
60  to  70  per  cent,  visible  light,  cuts  off  about  90  per  cent,  of  the  heat 

rays.  The  colour  of  this  glass 
is  pale  green.  The  author  has 
a  pair  of  goggles  fitted  with 
plain  lenses  of  this  glass  and 
has  found  them  invaluable 
when  operating  on  high-tem- 
perature work.  There  are, 
also,  gold-fitted  glasses  which 
are  superlatively  efficient 
in  absorbing  and  reflecting 
the  infra-red  heat  rays.  A 
sample  of  the  "  pfund  gold 
glass  "  previously  referred  to 
was  found  by  careful  test  to 
transmit  only  0-8  per  cent, 
of  the  heat  rays  generated  by 
a  200-watt  gas-filled  tung- 
sten lamp  operated  at  normal 
voltage,  the  temperature  of 
the  tungsten  spirals  being 
estimated  at  2,400°  C.  This 
glass  transmits  light  of  a 
green  colour  and  is  much 
darker  than  the  corning  G 
124  J,  so  it  probably  passes 
not  more  than  20  per  cent,  of 
the  visible  rays.  The  novi- 
weld  glasses,  especially  those  of  dark  tints,  are  also  very  efficient 
shields  against  the  infra-red  rays.  The  effects  of  even  low-power 
heat  rays,  when  generated  in  close  proximity  to  the  eyes  for  a 
considerable  time,  are  often  serious,  as  is  evidenced  by  the  fact 
that  glass-blowers  who  use  their  unprotected  eyes  near  to  hot 
gas  flames  of  weak  luminous  intensity,  are  frequently  afflicted  with 
cataract,  which  might  be  positively  avoided  by  wearing  spectacles 
made  with  plain  lenses  of  the  G  124  J  glass  or  its  equivalent. 


FIG.  128.— GOGGLES:  47  H,  48  H,  49  H. 


EYE  -PROTECTION  IN  IRON  WELDING  OPERATIONS    255 

Table  I.  indicates  roughly  the  percentage  of  heat  rays  transmitted 
by  various  coloured  glasses  of  given  thickness.  The  source  of  heat 
used  was  a  200-watt  gas-filled  Mazda  lamp  operating  at  a  temperature 
of  about  2,400°  C.  Although  substantially  correct  for  the  samples 
tested,  they  would  necessarily  vary  somewhat  for  other  samples 
of  different  thickness  and  degrees  of  coloration,  so  that  they 
can  be  taken  only  as  a  general  guide  for  comparative  purposes. 

TABLE  I. 


Kind  of  Glass.  Th  iclcness  in  Inches.  , 


Clear  white  mica 

0-004 

81 

Clear  window  glass 

0-102 

74 

Flashed  ruby 

0-097 

69 

Belgian  pot-yellow 

0-126 

50 

Cobalt-blue 

0-093 

43 

Emerald-green    .  . 

0-1 

36 

Dark  mica 

0-007 

15 

Corning  G  124  J  glass   . 

0-095 

10 

Dark  noviweld    .  . 

0-096 

4 

Pfund  gold  plated 

0-114 

I 

0-8 

We  now  come  to  the  invisible  ultra-violet  rays,  which  are  princi- 
pally to  be  feared,  not  only  because  they  are  invisible,  but  because, 
as  previously  stated,  we  have  no  organ  or  sense  for  detecting  them, 
and  we  can  only  trace  their  existence  by  their  effects.  In  all  cases, 
however,  when  we  are  forewarned  of  their  presence  they  are  very 
easily  shielded,  for  there  are  only  a  few  substances  which  are  trans- 
parent both  to  the  visible  light  and  to  ultra-violet  radiation.  Fore- 
most among  these  latter  substances,  because  it  is  most  common,  is 
clear  natural  quartz,  or  rock  crystal,  from  which  the  so-called 
"  pebble  "  spectacle  lenses  are  made. 

Fluorite  and  selenite  are  also  transparent  to  ultra-violet  rays, 
but  these  crystalline  minerals  are  rare  and  not  in  common  use. 
However,  a  moderate  thickness  of  ordinary  clear  glass,  sheets 
of  clear  or  amber  mica,  are  opaque  to  these  dangerous  rays.  As  a 
case  in  point,  it  is  well  known  that  the  mercury  vapour  lamp,  when 
made  with  a  quartz  tube,  is  an  exceedingly  dangerous  light  to  the 
eye,  being  a  prolific  source  of  ultra-violet  radiation,  so  that  when  it  is 
used  for  illumination  it  is  always  carefully  enclosed  in  an  outer  globe 
of  glass ;  when  the  mercury  vapour  lamp,  however,  is  made  with 
a  clear  glass  tube,  it  is  a  harmless  if  not  very  agreeable  source  of 
light,  because  the  outer  tube  of  clear  glass  is  opaque  to  the  ultra- 


256  MODERN  METHODS  OF  WELDING 

violet  rays  that  are  generated  abundantly  within  it  by  the  highly 
luminous  mercury  vapour. 

When  operating  with  a  source  of  light  which  is  known  to  be  rich 
in  ultra-violet  rays,  such  as  the  iron  arc  in  welding  operations,  it  is 
not  sufficient  to  guard  the  eyes  with  ordinary  spectacles,  because 
these  invisible  rays  are  capable  of  reflection  just  the  same  as  visible 
light,  and  injury  may  easily  ensue  from  slanting  reflections  reaching 
the  eyes  behind  the  spectacle  lenses.  Goggles  that  fit  closely  around 
the  eyes  are  the  only  sure  protection  in  such  cases.  Also,  when 
using  a  hand  shield,  such  as  that  shown  in  Fig.  124,  the  shield  should 
be  held  close  against  the  face  and  not  several  inches  from  it. 

It  may  here  be  mentioned  that  the  ultra-violet  rays,  when  they 
are  not  masked  or  overpowered  by  intense  visible  light,  produce 
the  curious  visible  effect  termed  "  fluorescence  "  in  many  natural 
and  artificial  compounds — that  is,  these  rays  cause  certain  com- 
pounds to  shine  with  various  bright  characteristic  colours,  when 
by  visible  light  alone  they  may  appear  pure  white,  or  of  some  weak 
neutral  tint.  Thus,  natural  willemite,  or  zinc  silicate,  from  certain 
localities  (which  may  also  be  made  artificially)  shows  a  bright  green 
colour  under  the  light  from  a  disruptive  spark  between  iron  terminals, 
whereas  this  compound  is  white,  or  nearly  so,  by  visible  light.  Also, 
all  compounds  of  salicylic  acid,  such  as  the  sodium  salicylate  tablets 
which  may  be  bought  at  any  drug  store,  are  pure  white  when  seen 
by  visible  light,  but  show  a  beautiful  blue  fluorescence  under  ultra- 
violet rays.  Many  other  chemical  compounds  could  be  mentioned 
which  possess  this  curious  property,  but  the  above  substances  will 
suffice  to  illustrate  the  effect  of  fluorescence  produced  by  ultra- 
violet rays  and  by  which  these  rays  may  be  detected.  It  must, 
however,  be  noted  that  these  substances  will  only  show  their  fluores- 
cent colours  very  faintly  when  viewed  by  the  light  of  low-tension  iron 
arc  used  in  welding,  because  the  intense  light  of  this  arc  will  over- 
power the  weaker  effect  of  the  invisible  ultra-violet  rays.  The  true 
beauty  of  fluorescent  colours  can  only  be  seen  under  a  high-tension 
disruptive  discharge  between  iron  terminals,  the  invisible  light  in 
this  case  being  weak  while  the  ultra-violet  rays  are  comparatively 
intense. 

Summarising  the  effects  of  means  for  eye-protection  against 
various  harmful  radiations,  particularly  associated  with  welding 
operations : 

(1)  The  intense  glare  and  flickering  of  the  visible  rays  should  be 
softened  and  toned  down  by  suitable  coloured  glasses  selected  by 
an  expert  and  having  a  depth  of  coloration  which  shows  the  clearest 


EYE-PROTECTION  IN  IRON  WELDING  OPERATIONS     257 

definition  combined  with  sufficient  obscuration  of  glare,  which  last 
feature  can  best  be  determined  by  the  individual  operator. 

(2)  When  infra-red  rays  are  present  to  a  dangerous  degree  a 
tested  heat-absorbing  or  heat-reflecting  glass  should  be  employed, 
either  in  combination  with  a  suitable  dark-coloured  glass,  when  a 
glaring  visible  light  is  present,  or  by  itself  in  cases  where  the  visible 
rays  are  not  injuriously  intense. 

(3)  In  guarding  the  eye  from  dangerous  ultra-violet  rays  it  must 
be  no  ted  carefully  that  "peb- 
ble "  lenses  are  made  from 

clear  quartz,  or  natural  rock 
crystal,  and  this  material,  be- 
ing transparent  to  these  rays, 
offers  no  protection  against 
their  harmful  features.  On 
the  other  hand,  ordinary 
clear  glass  is  a  protection 
against  these  rays  when  they 
are  not  very  intense,  but 
dark  amber  or  dark  amber- 
green  glasses  are  absolutely 
protective.  Glasses  showing 
blue  or  violet  tints  should 
be  avoided  except  in  certain 
combinations  wherein  they 
may  be  used  to  obscure  other 
colours. 

No.  47  H  goggles  are  light, 
rust-proof,  sanitary,  strong, 
and  perfectly  fitting.  They  are  fitted  with  essentialite  amber- 
coloured  lenses  which  afford  full  protection  to  the  eyes  and  cover- 
glasses  which  protect  coloured  lenses. 

O  -L 

No.  48  H  goggles  have  the  wire  shield  and  other  metal  parts 
covered  with  chamois ;  nose-piece  is  soft  leather. 

No.  49  H  goggles  have  aluminium  frame,  are  very  light  in 
weight,  and  are  exceedingly  popular  with  welders. 

No.  65  H  spectacles  have  a  nickelled  steel  frame  and  flexible 
ear-holds.  Fitted  with  amber  lenses,  they  are  very  light  and  com- 
fortable to  wear. 

No.  76  H  spectacles  are  fitted  with  essentialite  amber  lenses, 
have  flexible  ear-holds  and  light  fibre  frame,  making  them  very 
popular  with  welders  doing  light  work. 

17 


FIG.  129.— GOGGLES:  65  H,  76  H. 


CHAPTER    XXXIX 
MIRROR  WELDING 

MIRROR  welding  is  used  in  some  of  those  rare  cases  where  breaks  and 
fracture  occur  in  inaccessible  places,  in  which  ordinary  methods 
could  not  be  adopted.  This  method  is  quite  a  new  one,  and  not 
known  to  many,  and  it  is  useful  in  many  cases  where  dismantling 
would  have  to  take  place  in  ordinary  welding.  It  is  used  where  the 
space  between  the  article  for  welding  and  the  obstructing  surface 
is  too  small. 

The  operator  is  not  able  to  get  between  the  two  surfaces,  nor 
could  the  article  be  turned.  Sometimes  two  or  three  mirrors  are 
used  together,  and  set  at  different  angles,  so  as  to  facilitate  ease  in 
welding,  and  this  adjustment  has  to  be  made  very  accurately  so  that 
the  operator  can  do  the  welding  with  ease,  with  the  welding  line 
always  in  view.  It  is  very  important  that  the  operator  has  every- 
thing in  proper  order  and  in  the  exact  position  for  welding,  so  that 
during  the  welding  there  should  be  no  stopping. 

It  may  occur  in  some  instances  where  the  welding  has  to  be  done 
in  higher  places  than  ordinary  ones.  Precautions  must  therefore 
be  taken  to  secure  stability  of  the  structure  used. 

In  most  cases  of  mirror  welding,  dissolved  acetylene  compressed 
in  cylinders  (the  same  as  oxygen)  is  used.  Usually  these  repairs 
are  far  from  the  factory,  and  in  places  where  an  acetylene  generator 
would  not  be  allowed.  In  case  the  dissolved  acetylene  is  used,  an 
acetylene  regulator  would  be  required  for  the  acetylene  cylinder. 
These  acetylene  regulators  have  a  left-hand  screw  at  the  coupling, 
and  the  regulator  is  painted  red,  so  as  to  distinguish  them  from  the 
oxygen  regulators  (painted  black). 

The  operator  must  study  carefully  the  whole  job  that  he  has 
in  hand,  seeing  whether  it  is  necessary  to  preheat  the  article  and 
to  guard  against  unequal  and  invisible  stresses  and  strains.  See 
if  the  metal  is  J  inch  thick  or  over ;  if  so,  it  must  be  bevelled :  in  the 
instance  which  we  are  referring  to  it  would  be  difficult  to  bevel. 
Hence,  if  a  sound  weld  is  to  be  made  the  bevelling  must  be  accom- 
plished. It  can  be  done  by  the  cutting  blowpipe,  which,  if  the  handle 

258 


MIRROR  WELDING 


259 


of  the  cutter  is  held  parallel  to  the  pipe  now  being  welded,  and  the 
cutter  head  pointed  at  45  degrees  to  the  point  of  welding,  will 
bevel  one  side  of  the  line  of  welding ;  the  cutter  should  now  be  taken 
to  the  opposite  side  and  the  operation  repeated.  This  should  be 
clear  of  oxide  before  starting  to  weld. 

In  welds  of  this  description  there  must  be  two  operators,  one  eacli 


FIG.  130. — SHOWING  THE  PEINCIPLE  or  MIRROR  WELDING  WITH  SPECIALLY 
ARRANGED  FILLER  ROD. 

side,  one  using  the  blowpipe  and  the  other  the  welding-rod.  Special 
care  must  be  taken  by  both  operators  in  the  finding  of  the  correct 
point  on  the  line  of  welding  through  the  mirrors,  and  must  not,  under 
any  circumstances,  withdraw  their  visions  from  the  mirrors  until 
the  welding  line  has  been  completed. 

A  smaller  blowpipe  than  usual  should  be  used,  as  in  all  vertical 
and  overhead  welding  the  melted  metal  must  not  get  overheated 


260 


MODERN  METHODS  OF  WELDING 


or  it  will  become  too  fluid,  will  not  adhere,  will  fall  from  the  weld, 
and  the  metal  will  be  burnt  and  cause  a  larger  space  to  be  filled  up, 
and  it  would  be  oxidised,  burnt,  and  cinderised. 

All  that  is  necessary  is  to  heat  as  small  a  surface  as  possible,  not 
more  than  J  inch  from  the  bevel  (only  heat  the  outer  surface  to 
about  1,000°  C.).  Before  starting  to  do  any  welding  it  is  necessary 


FIG.  131. — MIEROR  AS  APPLIED  TO  THE  PIPE  HERETOFORE  DESCRIBED. 

to  see  that  all  the  equipment  is  in  perfect  order;  a  lighted  torch 
should  be  tried  to  see  for  certain  that  it  is  correct  for  proceeding. 

The  welding  should  be  commenced  at  |  inch  below  the  break  or 
fracture :  this  will  ensure  that  the  break  or  fracture  will  not  extend 
farther.  Assuming  that  one  has  got  all  correct,  and  the  trial  is 
satisfactory,  welding  should  now  go  forward,  remembering  that  one 
must  have  a  perfect  neutral  flame,  neither  oxidising  nor  carbonising, 
and  the  flame  must  be  kept  up  for  certaii  while  welding.  An 


MIRROR  WELDING  261 

oxidising  flame  causes  adhesion,  lack  of  penetration,   oxidation, 
burnt  and  cindered  weld,  and  the  tests  will  fail. 

The  welding-rod  must  be  absolutely  pure,  free  from  phosphorus, 
sulphur,  manganese,  and  other  impurities;  the  size  must  be  deter- 
mined by  the  thickness  of  the  metal  to  be  welded ;  several  rods  should 


FIG.  132. — INTERNAL  WELDING  OF  A  BOILER,  WITH  A  MIRROR. 

be  kept  at  hand  before  starting  welding.  Welding  may  now  be 
started;  the  blowpipe  must  be  kept  on  the  particular  welding  line 
until  such  time  as  the  bottom  is  melted,  when  the  bottom  is  found 
at  the  starting-point;  there  should  be  no  mistake  about  the  line 
being  continued  from  the  bottom  of  the  weld. 

The  welding  must  be  homogeneous,  starting  at  the  bottom  as 


262  MODERN  METHODS  OF  WELDING 

previously  stated,  and  as  soon  as  this  is  melted  add  welding-rod, 
previously  heated,  in  the  bevel  and  move  the  blowpipe  forward 
with  an  elliptical  sweep,  keeping  it  close  in  the  line  of  the  welding ; 
do  not  let  the  white  tip  touch  the  metal,  but  keep  it  |-  inch  from  it, 
and  go  steadily  forward,  filling  up  the  bevel  uniformly  with  the  feed- 
ing-rod until  the  end  of  the  weld  is  reached.  There  must  be  no 
stoppage  whatever,  while  welding  the  line  fractured.  If  it  is 
done  quickly  and  filled  in  as  the  welding  proceeds,  with  no  stoppage, 
the  weld  will  be  a  success — neat  and  strong. 

As  soon  as  the  welding  is  completed  it  is  necessary  that  it  be 
heated  to  950°  C.  and  allowed  to  cool  slowly,  free  from  air. 

The  mirror  welding  of  a  boiler,  as  shown  in  Fig.  132,  is  one 
that  needs  every  care  and  consideration;  more  so  than  the  pipe 
job  previously  referred  to,  because  a  boiler  has  to  stand  very 
severe  tests  and  strains  during  its  working  under  steam.  Another 
important  point  in  these  boiler  cases  is  expansion  and  contrac- 
tion and  the  avoiding  of  internal  and  invisible  strains.  In  the 
welding  of  this  boiler  it  must  first  be  made  thoroughly  clean;  all 
deposited  scale  that  has  accumulated  must  be  removed  from  the 
fracture  and  surroundings,  and  the  line  of  welding  must  be  filed 
to  remove  all  rust,  leaving  it  bright  and  smooth. 

Before  welding  can  take  place  it  is  necessary  to  preheat  a  large 
area  of  the  boiler  internally  so  that  the  expansion  and  contraction 
may  be  spread  over  a  larger  area  than  the  small  confines  of  the  weld. 
In  this  case  it  would  be  difficult  to  bevel  the  edges  of  the  fracture ; 
with  the  cutting  blowpipe,  therefore,  in  place  of  the  bevelling,  a  size 
larger  blowpipe  may  be  used  to  penetrate  right  through  the  metal. 

Before  preheating,  it  is  necessary  to  have  all  equipment  ready, 
the  mirrors  fixed  temporarily  and  marked  at  the  proper  angle,  and 
the  blowpipe  tried  in  position  for  welding.  This  preheating  should 
be  carried  out  by  putting  a  fire  inside  the  boiler  until  it  reaches  the 
temperature  of  950°  C.  When  this  temperature  is  reached,  immedi- 
ately put  back  the  mirrors  in  place  to  the  angle  previously  marked 
and  commence  welding  without  delay,  and  see  that  the  temperature 
does  not  get  below  800°  C.,  or  cracks  or  fractures  will  take  place. 

The  welding  should  be  started  at  J  inch  beyond  the  line  of  weld- 
ing so  as  to  prevent  the  crack  or  fracture  extending  farther  than  the 
present  line  of  welding.  It  is  not  necessary  to  have  two  operators 
on  a  job  like  this.  The  blowpipe  is  to  be  one  size  larger  than  is 
usual  for  the  thickness  of  metal  being  welded,  and  the  pressure  of 
oxygen  to  be  slightly  less  than  that  stated  on  the  blowpipe.  First, 
the  surroundings  of  the  crack  or  fracture  should  be  heated  to  about 


MIRROR  WELDING  263 

1,000°  C.,  a  little  above  the  preheating  temperature,  and  then  start 
welding  at  the  point  previously  referred  to ;  this  point  takes  more 
heating  than  the  other  part  of  the  welding  line. 

There  are  difficulties  of  lack  of  penetration,  bad  joining,  blow- 
holes, and  interposition  of  oxide.  Lack  of  penetration  is  a  frequent 
occurrence.  There  is,  however,  no  justification  for  this,  if  operators 
will  only  go  to  the  bottom  of  the  weld  in  all  cases.  Interposition 
of  oxide  is  a  common  occurrence,  and  all  operators  should  study 
this  and  make  test  pieces  until  they  are  satisfied  that  there  is  no 
interposition.  It  occurs,  chiefly,  with  excess  of  oxygen  and  using 
too  large  a  blowpipe.  The  oxide  formed  through  these  errors  is  im- 
prisoned in  the  metal.  It  is  very  important  to  see  that  during  the 
welding  no  adhesion  takes  place  and  full  penetration  has  been 
observed,  that  there  is  no  oxidation  nor  blowholes,  and  that 
no  part  of  the  weld  has  been  gone  over  twice  without  adding 
the  welding-rod.  When  the  welding  is  completed,  the  temperature 
should  be  immediately  taken,  and  whatever  it  is  it  must  be  raised 
to  950°  C.  by  putting  a  fire  in  the  boiler,  then  allowed  to  cool  slowly, 
free  from  air.  When  cold,  test  by  hydraulic  pressure  to  double 
the  working  pressure. 

Assuming  that  welding  is  now  starting,  the  operator  must  start 
just  below  the  fracture  line,  get  well  hot  over  an  area  of  3*x  3  inches 
before  melting  at  the  starting-point — this  will  increase  the  speed  of 
welding — penetrate  fully,  keeping  the  tip  of  the  blowpipe  vertical 
and  at  an  angle  of  40  degrees,  which  will  just  suit  the  fracture,  go 
along  slowly  and  regularly  with  a  gyratory  movement,  adding  the 
necessary  welding-rod,  filling  the  fracture  to  its  greatest  extent  with 
a  little  extra  coating  to  give  more  strength ;  be  sure  that  there  is  no 
stoppage ;  the  molten  metal  must  be  semiplastic  and  not  cinderised 
in  any  way,  or  too  fluid — just  at  a  temperature  that  will  scarcely 
run;  a  good  weld  will  then  be  obtained. 


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